“I saw it a million years ago, and I’m still upset about it.”

Oleksii bolted across the tarmac in the dark as the first Russian missiles landed, clambered into his Su-27 fighter jet and took off just as buildings across the airfield began to explode.

“At that moment, I understood that it was really something bad,” said Oleksii, 26, on condition that only his first name and rank, captain, be used. Some other soldiers and officials in this article were not authorized to speak publicly, or faced reprisals.

Just before 6 a.m. Moscow time, Mr. Putin declared the opening of his “special military operation” in a televised address. It began with an aerial bombardment to take out Ukraine’s air defenses, communications and radar installations — to overwhelm its military and shatter its ability to fight back.

More than 150 missiles thundered into Ukraine from bombers, submarines and ships. As many as 75 Russian aircraft streaked into Ukrainian skies, about the size of Ukraine’s entire working air combat fleet, analysts and officials said.

On his radar screen, Oleksii saw the blips of incoming missiles and enemy aircraft before getting his orders: Fly to a backup air base in central Ukraine. When he landed, he was astonished. Not only was his unit there, but a good portion of Ukraine’s remaining air force as well.

For days, he and his fellow pilots flew missions from their new base, wondering when Russian radar operators would finally notice them. A strike on their position could have been disastrous, gutting the Ukrainian defense, and the pilots assumed it was only a matter of time until one came. But it took four days for the Russians to attack, and most of the aircraft had moved to new locations by then, leaving Oleksii in amazement.

“It was really simple,” he said. “I don’t know how they missed this opportunity.”

The failure to destroy Ukraine’s modest air defenses was one of the most significant blunders of the war, foiling Russia’s mighty air force early on. Interviews revealed why that happened — and how the Ukrainians managed to stay a step ahead of their invaders.

Ukraine should have been overwhelmed. By one count, its fighter jets were outnumbered 15 to one in some early air battles. Russia’s planes were also more advanced, helping its pilots see farther and strike from greater distances. Russia had thousands of cruise and ballistic missiles that should have smothered Ukraine’s aging, Soviet-era defenses. That is what American and Ukrainian intelligence officials assumed, anyway, leading to predictions that Ukraine would fall within days.

So, Ukraine shuffled the deck. It moved some of its defenses — like Buk and S-300 missile launchers, along with its primary radio intelligence command and control center — to new sites before the war began, senior Ukrainian officials said. Russian missiles often hit the old locations instead. In all, as many as 60 percent of Russian cruise missiles missed their intended targets, American officials said.

Part of Russia’s problem was agility. Even if Russian forces had spotted Oleksii and his fellow pilots bunched together at their new rendezvous point, American officials said, Russia’s military was so rigid and centralized that it typically needed 48 to 72 hours to update its intelligence and get approval to go after new targets — by which time the Ukrainians were gone.

That same inflexibility made the Russians easy to hit. After failing to take out Ukraine’s defenses, many Russian pilots kept flying as if they had. Their ground-attack planes often flew sorties without backup from other fighter jets, the Ukrainians said, enabling outgunned pilots like Oleksii to catch them off-guard by flying at low altitudes, hidden from radar, and roaring up from below to shoot them down.

The debris of a Russian Su-34 aircraft that crashed into a residential neighborhood in Chernihiv in March.

David Guttenfelder for The New York Times

“Maybe the Russian Army didn’t read the Soviet books,” Oleksii said. “They flew straight without any cover. They had bombs, they had rockets, but they didn’t cover their attack aircraft.”

Then in March, when Russian pilots finally changed tactics and started flying low enough to duck under Ukrainian air defense radar, they fell into the sights of Ukrainian missiles, including shoulder-fired Stingers provided by the United States.

For Russian troops on the ground, it was a disaster.

Without air cover, they were suddenly far more vulnerable, throwing their troubled march toward Kyiv and other large cities further into disarray.

Though tens of thousands of them had amassed along Ukraine’s borders, hovering menacingly as if eager to strike, many never thought they were actually going to war. Like most of Russia, they figured it was just for show, to extract concessions from the West.

Interviews with Russian soldiers show how stunned they were when the orders came to invade. Cpl. Nikita Chibrin, a 27-year-old soldier in a motorized infantry brigade, said he had spent the month before in Belarus on what he and his fellow soldiers were told was a training exercise. On Feb. 23, he said, he and his unit were at their camp celebrating the Defender of the Fatherland holiday, snacking on candy they had been given for the occasion, when their commander approached.

“Tomorrow you are going to Ukraine to fuck up some shit,” he said the commander told them. There was no further explanation.

Before dawn on the 24th, Corporal Chibrin and his comrades loaded into a tracked armored personnel carrier. They had no instructions and no idea where they were headed, he said.

Another Russian soldier stationed in Belarus said he found out he was going to war only an hour before his unit began to march. The order was both simple and wildly optimistic: Follow the vehicle in front of you and reach Kyiv within 18 hours.

According to the unit’s schedule and logbook — which were obtained by The Times and reviewed by three independent military analysts, who considered them authentic — the first vehicles in his convoy were supposed to punch down from Belarus and arrive on the outskirts of Kyiv by 2:55 p.m., even faster than the soldier was told.

He didn’t come close. The massive vehicles were so heavy, ripping up the roads as they tried to move forward, that the convoy got bogged down immediately, the soldier said. It took more than a day just to cross the border into Ukraine.

It got worse from there. The logbook recorded day after day of delays, Ukrainian attacks and hundreds of injuries, deaths and destroyed vehicles.

Secret orders for a different Russian force — obtained by The Times and shared with four independent military analysts, all of whom said they were credible — were issued only hours before Mr. Putin’s announcement.

The orders, for a unit of the 26th Tank Regiment, were oddly overconfident, to the point of being contradictory. They anticipated a tangle of possible resistance from Ukrainian troops and planes, yet they still laid out a mostly uninhibited, 24-hour dash from Ukraine’s border with Russia to a point across the Dnipro River, about 250 miles away.

There, the unit would dig in, about two hours outside Kyiv, and block Ukrainian troops sweeping in from the south and east, the Russian war plans said. And no matter how fierce the enemy was, the unit was expected to complete the mission on its own.

“There are no forces or equipment for reinforcements,” the orders said.

Sure enough, the lumbering, largely unprotected Russian columns proved enticing targets.

On March 17, Valeriy Zaluzhnyi, the commander of Ukrainian forces, posted a video of burning tanks that he said belonged to the 26th Tank Regiment in northeastern Ukraine — hundreds of kilometers short of its intended destination.

The unit lost 16 vehicles in less than three weeks, according to Russian documents seized and published by Ukraine. The mother of one young tank soldier on the unit’s roster told Russian media that her son was brought home in pieces, identified only by his DNA.

Across Ukraine, the Russian losses mounted. A giant armored column of more than 30,000 troops at the core of Russia’s force pushing south toward the city of Chernihiv was eviscerated by a motley group of Ukrainian defenders outnumbered five to one, soldiers and senior officials said. The Ukrainians hid in the forest and picked apart the Russian column with shoulder-fired antitank weapons, like American-made Javelins.

One Russian soldier in the unit said he was shocked by the swiftness of the Ukrainian attack.

“In the first battle, the column was ambushed, and I was wounded, and that’s it,” he said. “For 24 hours, I was missing a leg, lying in a field waiting for my unit to come get me.”

The rout near Chernihiv spoiled part of Russia’s plan to envelop Kyiv.

Ukrainian soldiers walking along a street where a column of Russian military vehicles was destroyed near Chernihiv in April.

Daniel Berehulak for The New York Times

A massacre at the Antonov Airport spoiled another.

Russian forces had counted on the element of surprise when wave upon wave of helicopters descended on the airport, home to the largest aircraft in the world: the An-225 Mriya, a cargo plane with a 290-foot wingspan that was an object of Ukrainian national pride.

Taking the airport would give Russian forces a beachhead to ferry in troops for the assault on Ukraine’s capital. But the Ukrainians expected as much. Using shoulder-fired missiles, they shot down Russian aircraft and killed as many as 300 Russian paratroopers, according to senior American and Ukrainian officials and the captured Russian logbook.

Fierce battles in the following days destroyed much of the airport, including the prized Mriya cargo jet, but thwarted Russia’s plans.

“Yes, we lost our Mriya,” said Col. Yuriy Ignat, the spokesman for Ukraine’s Air Force Command. “But as a result the airport wasn’t lost.”

Russia not only botched the attack by land and air, but also put too much faith in another wing of its vaunted arsenal: hacking.

Even before the first missiles and shots were fired, unit 74455 of the Russian Military Intelligence Directorate, or G.R.U., tried to infiltrate Ukrainian networks and shut them down.

Officials in Washington, who had been working closely with the Ukrainians to bolster their cyberdefenses for years, had been holding their breath. States had mainly used hacking for acts of espionage and financial thievery, for subversion and sabotage. But nobody really knew how it would play out in a full-scale military conflict.

“All this stuff that has been written about cyberwar has been speculative,” said a senior U.S. defense official. “For the first time, you have war and cyber together — the real thing.”

The Russian hacking unit, known as Sandworm, had long menaced Ukraine, waging attacks against the power grid starting in 2015. But it was labor intensive, and only somewhat effective. By one estimate, it took Sandworm about 19 months to prepare the attack on a power station in western Ukraine, yet it only caused a six-hour power outage.

A cyber cat-and-mouse game ensued, with the United States, Britain and other allies helping to shore up Ukrainian computers and stave off Russian intrusions.

On Feb. 23, hours before the invasion began, Sandworm took another swing, launching malware that infected several hundred Ukrainian government computers, officials said. The intrusion was detected quickly, the damage contained.

Then Sandworm struck again. But the code it used looked like it had been thrown together at the last minute, with programming errors — another fail.

Sandworm wasn’t done. In its boldest stroke yet, it went after the Ukrainian military’s satellite communications, used by soldiers in the field. It worked, and by 6:15 a.m. on Feb. 24, the system went down, right at Ukraine’s most vulnerable moment.

It could have been a crippling blow. But the Ukrainian government had a backup plan: a separate satellite communications system, which it had tested only two months before, to make sure it was ready in the event of a Russian invasion.

Russia had assumed its forces would march largely uncontested into Kyiv. When that didn’t happen, American officials suspect that Sandworm — like the rest of the Russian military — was caught off guard.

Soon, Russia’s missteps went from the sophisticated to the mundane.

With their plans for a speedy victory stymied, Russian forces were suddenly confronted with the most basic of problems: They hadn’t brought enough food, water or other supplies for a prolonged campaign. Soldiers resorted to looting grocery stores, hospitals and homes.

“The guys were going from apartment to apartment and taking out large bags — looting in all its glory,” one Russian soldier wrote in mid-March in his diary, which was recovered by Ukrainian troops in eastern Ukraine and shared with a Times reporter embedded with them. “Some take only what they need, some take everything, from old nonfunctional phones to plasma TVs, computers, and expensive alcohol.”

In the diary, the soldier recounts hunting for medicine, food and other essentials, describing the joy his men felt entering a grocery store.

“We found everything that we lacked so much, even sweets,” the soldier wrote. “Everyone rejoiced like children.”

He recounts nearly dying in a mortar attack and stalking a Ukrainian armored personnel carrier. But just as often, he appears concerned with basic provisions for himself and his comrades, describing how they scoured a hospital and came up with jam, cookies and raisins.

Two days later, he had more luck. “I found socks that are now worth their weight in gold,” he wrote.

Some Russian troops panicked, and even resorted to self-sabotage. One Pentagon intelligence report said that Russian military drivers were poking holes in their gas tanks, disabling their own vehicles to avoid going into battle.

The commander of a Ukrainian tank repair depot said some 30 Russian T-80 tanks in seemingly perfect condition were taken and delivered to him at the beginning of the war. When his mechanics inspected, they found sand had been poured into the fuel tanks, rendering them inoperable.

Ukrainian law enforcement officials started noticing something else suspicious as well: a spike in foreign cellphone numbers near the border, in the forests between Ukraine and Belarus.

Russian soldiers were using cellphones to call home, and suddenly popping up on Ukrainian networks. Officials who monitor the traffic during peacetime for criminal activity quickly realized they could see and hear the invaders approaching in real time.

“We listened to the Russian soldiers as they panicked and called their friends and relatives,” said an official who oversees the phone intercepts. “They used ordinary phones to make decisions about their further moves.”

Down long corridors guarded by locks with facial detection, behind doors sealed with wax to detect intruders, teams of women tracked the Russian troops from small listening booths while their friends and relatives grabbed rifles to patrol the streets.

“We understood where the enemy was, what numbers they were using,” the official said.

The eavesdroppers passed the details to Ukraine’s armed forces to carry out ambushes and counterattacks. Maj. Gen. Kyrylo Budanov, the head of Ukraine’s military intelligence, said Ukrainian forces used cellphone signals and even TikTok videos to target a unit of Chechen soldiers known as the Kadyrovtsy, named for the strongman leader of Chechnya, Ramzan Kadyrov.

It took 40 minutes from the time one video was uploaded to pinpoint the unit’s location near the Hostomel airport northwest of Kyiv, Mr. Budanov said. The Ukrainian military then hit them with three Tochka-U ballistic missiles, he said.

The Russians kept closing in on Kyiv, forcing the eavesdroppers tucked in listening rooms to make a quick decision: destroy their equipment and flee for their own safety, or hang on and continue gathering intelligence.

They stayed.

“We didn’t lose Ukraine. We didn’t let the enemy move further,” the official said. “On the first days, when they made foolish mistakes, we used their foolish mistakes to our advantage.”

William J. Burns, the director of the C.I.A., flew to Moscow, sat in a conference room near the Kremlin and waited until the formalities were over before explaining the real reason he had come.

It was early November 2021. The United States believed Mr. Putin was considering a full-scale invasion of Ukraine, Mr. Burns explained. If he proceeded down this path, Mr. Burns warned, the West would respond — decisively, in unison — and the consequences for Russia would be severe.

Nikolai Patrushev, the secretary of Mr. Putin’s security council, stiffened and looked Mr. Burns in the eye, officials in the room said. He abandoned his notes and extolled the prowess of Russia’s armed forces. They had been so thoroughly modernized under Mr. Putin that they now rivaled the United States militarily, he said.

“Patrushev didn’t qualify it,” said John Sullivan, the American ambassador to Russia at the time, who was there. “He was just looking at Burns and saying: ‘We can do this. We’re back.’ The way I would describe it was that this was already decided, and they were supremely confident. His message was, ‘It’s not going to be a problem for us to do what we want to do.’”

Mr. Burns briefed Mr. Biden upon his return to Washington, officials said. Mr. Putin had all but made up his mind to take over Ukraine, Mr. Burns told him, and the Russians had absolute confidence victory would come swiftly.

To Mr. Putin, Ukraine is an artificial nation, used by the West to weaken Russia. He describes it as a cradle of Russian culture, a centerpiece of Russian identity that must be wrested back from the West and returned to Russia’s orbit.

In his eyes, that is the biggest unfinished mission of his 22 years in power, people who know him say.

He began as an unassuming bureaucrat-turned-president on New Year’s Eve, 1999, seen by the inner circle of his predecessor, Boris N. Yeltsin, as a proficient manager who could bring stability without threatening the ruling elite.

By his third decade in power, Mr. Putin seems transformed, people who have known him since the 1990s say. He styles himself as a pivotal figure astride a millennium of Russian history — as he hinted when he unveiled a statue of Vladimir the Great, the medieval prince of Kyiv, outside the Kremlin walls in 2016.

That Vladimir “entered history as a uniter and protector of Russian lands,” Mr. Putin said.

The Vladimir at Russia’s helm in the 21st century, Mr. Putin has increasingly made plain, sees himself as carrying on that tradition.

“If everyone around you is telling you for 22 years that you are a super-genius, then you will start to believe that this is who you are,” said Oleg Tinkov, a former Russian banking tycoon who turned against Mr. Putin this year. “Russian businesspeople, Russian officials, the Russian people — they saw a czar in him. He just went nuts.”

Mr. Putin rose to power as a deft politician. He could flash charm, humility and a smile, painting himself as a reasonable leader to Russians and foreigners. He knew how to control his facial muscles in tense conversations, leaving his eyes as the only guide to his emotions, people who know him said.

But during his presidency, he increasingly wallowed in a swirl of grievances and obsessions: the West’s supposed disregard for the Soviet Union’s role in defeating Nazi Germany; the fear that NATO would base nuclear missiles in Ukraine to strike Moscow; modern-day gender politics in which, Mr. Putin often says, Mom and Dad are being replaced by “Parent No. 1 and Parent No. 2.”

In the personalist system he has built, those quirks have global consequences.

“What he thinks about obsessively, and quite possibly falsely,” has ended up shaping “the biography of the whole world,” said Konstantin Remchukov, a Moscow newspaper editor.

Mr. Putin seemed to think that only he truly understood Ukraine. After annexing the Ukrainian peninsula of Crimea in 2014, Mr. Putin bragged that he had overruled his own advisers, who had considered the move too dangerous because of the risk of sanctions and a Ukrainian military response.

Back then, Mr. Putin’s instincts mostly proved right. The Ukrainian military withdrew swiftly from Crimea — some soldiers and sailors switched sides to join Russia — and the West’s limited sanctions scarcely affected Russia’s economy, sealing Mr. Putin’s confidence.

“I took responsibility for everything,” Mr. Putin said after taking Crimea, according to a confidant. “I will be gone sooner or later, but Crimea will have been returned to Russia forever.”

A pro-Russian rally on Crimea in 2014, the year Russia seized the peninsula.

Sergey Ponomarev for The New York Times

Many of the people closest to Mr. Putin had an incentive to cater to the boss’s rising self-regard — and to magnify the external threats and historical injustices that Mr. Putin saw himself as fighting against.

A former Putin confidant compared the dynamic to the radicalization spiral of a social media algorithm, feeding users content that provokes an emotional reaction.

“They read his mood and they start to slip him that kind of stuff,” he said.

By the summer of 2021, during a meeting that was supposed to be about the economy, Mr. Putin railed instead against the West and President George W. Bush’s withdrawal from the Antiballistic Missile Treaty in 2002, which Mr. Putin often cites as one of America’s great post-Cold War sins.

“We tried to partner with the West for many years, but the partnership was not accepted, it didn’t work,” Mr. Putin said, recalled his guest, who sat on the other end of a long table.

The words had a sort of finality to them, the visitor said: “It was like he was talking to himself, not to me.”

The guest had spent three days in quarantine before meeting with Mr. Putin at a distance of roughly 15 feet. It was a “light” option the Kremlin offered to people who sought face time with Mr. Putin but wanted to avoid the lengthy quarantines required for an up-close meeting with him, even in the pandemic’s second year.

Mr. Putin meeting with his defense minister and a top military official in February. The photo was released by Russian state media.

Aleksey Nikolskyi/Sputnik, via Reuters

Mr. Putin’s isolation deepened his radicalization, people who know him say. He went 16 months without meeting a single Western leader in person. He held just about all his meetings by videoconference from nondescript rooms that left his exact location a mystery. Those who got to see him in person saw their influence rise in a system in which access to Mr. Putin — referred to as “the boss” or “V.V.,” his first initials, by insiders — is the most valuable of currencies.

“Our most important resource is not a medal, not money and not possession of anything,” said Konstantin Zatulin, a member of Parliament in Mr. Putin’s United Russia party. “Our main, most important resource is access to the president.”

On that score, Yuri Kovalchuk, a conservative physicist and banking magnate who befriended Mr. Putin in the 1990s, did well during the pandemic. Mr. Kovalchuk bragged last year that he had spent several months in 2020 with Mr. Putin at his residence on Lake Valdai, between St. Petersburg and Moscow, according to a person who met with him then.

Mr. Kovalchuk told the person that Mr. Putin’s main achievement was “militarization” — the creation of an army and a society ready for war.

The secretive Mr. Kovalchuk prides himself as a strategist who sees Russia locked in an existential battle with the West, according to people who know him. In the last decade, he has expanded his television and newspaper holdings, key parts of the Kremlin’s propaganda apparatus.

A onetime Putin confidant said Mr. Kovalchuk sees himself “as a visionary,” and the pandemic, given the extraordinary precautions Mr. Putin took, emerged as an opportunity for Mr. Kovalchuk to deepen his imprint on the president — and the nation.

Mr. Putin’s unfinished business with Ukraine also fed a growing personal animus toward Ukraine’s president, Volodymyr Zelensky.

Ukraine’s president, Volodymyr Zelensky, at a news conference in Kyiv in March.

Lynsey Addario for The New York Times

When Mr. Zelensky was elected in a landslide in 2019, the Kremlin saw him as someone it could work with: a Russian-speaking comedian who had lived in Moscow, performed on Russian television and won with a message of ending the war in eastern Ukraine that Russia had fueled.

And partly because Mr. Zelensky is Jewish, some in Moscow expected him to be tough on Ukraine’s nationalist wing, which venerated Ukrainian independence fighters who had fought alongside the Nazis in the closing battles of World War II.

“I think he is sincerely willing” to compromise with Russia, Mr. Putin said of Mr. Zelensky in 2019. “It is his sincere conviction, at least his striving.”

By early 2021, the Kremlin’s hopes had been dashed. Mr. Zelensky cracked down on pro-Russian interests in Ukraine, shutting down pro-Russian television channels and sanctioning Viktor Medvedchuk, a Ukrainian oligarch close to Mr. Putin.

Mr. Putin showed his frustration in a long meeting at his Sochi residence with Mr. Bennett, the new prime minister of Israel, in October 2021.

Mr. Putin charmed his guest, taking him into his private residence and pouring him a glass of whiskey. But when it came to Ukraine, Mr. Putin flashed anger. Mr. Bennett noted that Mr. Zelensky was interested in meeting Mr. Putin face to face.

“I have nothing to discuss with this person,” Mr. Putin shot back, according to two people familiar with the exchange. “What kind of Jew is he? He’s an enabler of Nazism.”

Some Western officials believe that, by that point, Mr. Putin may have already decided to go to war. But in Russia, even among those with access to Mr. Putin or his inner circle, almost no one thought that the president was seriously considering a full-scale invasion, people close to the Kremlin said. They were sure he was bluffing.

Mr. Remchukov, the newspaper editor, was one of them. As the chairman of the 2018 election campaign of Mayor Sergei S. Sobyanin of Moscow — Mr. Putin’s former chief of staff — he felt well-connected enough to happily announce to his wife a week before the invasion, “Lena, there won’t be a war!”

That day, he had met for two hours with several senior military officials. Rather than betray any hint of tension, they bantered about Mr. Remchukov’s newly svelte physique, queried him in detail about his weight-loss regimen and casually discussed their vacation plans for early March.

After he came home and described the meeting to his wife, he said, “she kissed me and said: ‘What happiness!’”

The Americans, by contrast, feared the worst.

On Feb. 22, two days before the invasion, Ukraine’s foreign minister, Dmytro Kuleba, went to the Pentagon and said his nation desperately needed Stingers, the shoulder-fired antiaircraft missiles.

Secretary of Defense Lloyd J. Austin III offered to help before asking how the Ukrainian government planned to keep running after the Russians invaded. “If you get pushed out of Kyiv,” he said, “where are you going to go?”

Mr. Kuleba replied: “I can’t even acknowledge that. We’re not even going to talk about that or think about that.”

“Yeah, I got that,” Mr. Austin said. “But you need a plan.”

Soon, Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, joined in, launching into what a senior American defense official described as a “‘you’re going to die’ speech.”

“They’re going to roll into Kyiv in a few days,” General Milley said. “They’re coming in with tanks and columns of formations. You need to be ready for that. You need to be prepared. If you’re not, it’s going to be a slaughter.”

As General Milley spoke, Mr. Kuleba and members of his delegation sat back in their chairs, their eyes widening.

The Ukrainian air force had trained with NATO members since 2011, and the partnership deepened after Russia took Crimea in 2014. Wary of another invasion, they carried out combat exercises in Ukraine and California, preparing the nation’s air force to take on its technologically superior enemy. In February, a secretive U.S. Air Force and Air National Guard team called Grey Wolf was set up at Ramstein Air Base in Germany to support the Ukrainians.

But General Milley still harbored serious doubts about Ukraine’s state of readiness. He had walked the halls of the Pentagon that winter with an enormous green map of Ukraine, with increasingly ominous projections from U.S. intelligence agencies of Russia’s invasion plans. What’s more, the American defense attaché at the embassy in Kyiv had spent weeks trying to get Ukraine’s defensive plans, and the ones she received minimized, in the Pentagon’s view, the Russian threat.

Mr. Austin seemed somewhat uncomfortable at General Milley’s blunt admonishment of the Ukrainian foreign minister and chimed in, reassuringly: “We’re going to do what we can to help these guys.”

The reality was slow to sink in for many in Moscow, too. Mr. Zatulin, a senior Putin ally in Russia’s Parliament, said he got his first inkling that the president was serious about an invasion in mid-February. Though known as a leading expert on Ukraine, Mr. Zatulin said he was never consulted on the possibility.

To the contrary, Mr. Zatulin said he was scheduled to give an address to the Russian Parliament on behalf of Mr. Putin’s United Russia party on Feb. 15 that was supposed to signal the opposite — that there would be no invasion unless Mr. Zelensky himself went on the offensive in Ukraine’s divided east. But just five minutes before the session was scheduled to start, Mr. Zatulin said, he got a message from an aide: The party’s leadership had canceled his speech.

“I was not ready for this turn of events,” Mr. Zatulin said. “Everything connected to this decision turned out to be a surprise not just for me, but also for a great many of the people in power.”

Mr. Peskov, Mr. Putin’s spokesman, insisted that he found out about the invasion only once it had begun. Likewise, Anton Vaino, Mr. Putin’s chief of staff, and Aleksei Gromov, Mr. Putin’s powerful media adviser, also said they did not know in advance, according to people who spoke to them about it.

The best that senior aides could do was to try to read Mr. Putin’s body language. Some reported with concern that “he’s got this warlike twinkle in his eyes,” a person close to the Kremlin said.

Russian howitzers being loaded onto train cars at a station outside Taganrog, Russia, days before the invasion.

The New York Times

Sergei Markov, a former Kremlin adviser, said that amid Russia’s military buildup around Ukraine late last year, a deputy minister asked him if he knew what was going to happen.

“That means that no one has told the deputy minister,” Mr. Markov said. “Even some members” of Russia’s security council “weren’t told until the last moment.”

Many elites found out too late.

Russia’s main industrial association had been expecting to meet with Mr. Putin in February. On the agenda, among other things: the regulation of cryptocurrencies. But the meeting kept getting rescheduled, until finally, on Feb. 22 or Feb. 23, the Kremlin notified participants of the date: Feb. 24, the day Mr. Putin invaded Ukraine.

Andrey Melnichenko, a coal and fertilizer billionaire in that lobbying group, described how he woke up that day to the “madness” in Ukraine. But the meeting with Mr. Putin was still on, so a few hours later, he was at the Kremlin, as scheduled. In an anteroom, stunned tycoons were munching on sandwiches while awaiting the results of their coronavirus swabs to clear them to share Mr. Putin’s air.

When Mr. Putin finally appeared, the television cameras were rolling. He told the assembled billionaires that he had no choice but to invade.

“What happened, in my view, is irrational,” said Mr. Melnichenko, describing his reaction to the invasion. “It was shock.”

Another magnate recalled realizing — too late — that Mr. Putin was parading them in front of the television cameras, for all the world to see, for a carefully planned purpose. The point was “specifically to tar everyone there,” he said, “to get everyone sanctioned.”

There was no going back. They, like the rest of Russia, were in this with Mr. Putin now.

Sure enough, Mr. Melnichenko and all the other businessmen who appeared with Mr. Putin that day were hit with sanctions by the West in the months that followed.

The messages, drawn from tens of thousands of emails leaked from Russia’s largest state-owned media company and reviewed by The Times, show how at least one engine of the Russian war effort purred along smoothly: the nation’s propaganda machine.

At times, Russia’s military and the F.S.B. directed coverage down to the video clips played and the time of publication. The emails, leaked from V.G.T.R.K., the state media giant that oversees some of Russia’s most-watched channels, portrayed Mr. Putin’s military as backed into a corner by NATO.

Once the full invasion began, the machine downplayed Russian atrocities, bolstered conspiracy theories and tried to portray Ukrainian troops as abandoning their posts. (After the emails were released by a group that publishes hacked documents, The Times verified the documents by confirming identities, email addresses and broadcasts on the air.)

Off camera, state media employees had little to no idea what was actually happening. A state television journalist said in an interview that as late as April, his Kremlin sources were still assuring him that the war would be over within days.

“Tomorrow morning, there’ll be a statement,” the journalist recalled one of his sources saying, only to be proved wrong the next day. “It was really kind of weird.”

But while state broadcasters kept delivering upbeat assessments, Mr. Putin privately acknowledged that his military was struggling.

During the meeting in March with Mr. Bennett of Israel — when Mr. Putin conceded that the war would be “much more difficult than we thought” — he returned to the theme that has become a fixation of his presidency: his place in Russian history.

“I won’t be the Russian leader who stood by and did nothing,” he told Mr. Bennett, according to two people familiar with the exchange.

Once again, Mr. Putin seemed convinced that future generations of Russians could be threatened by the West. He had spent years preparing for precisely such a clash, devoting hundreds of billions of dollars to Russia’s military, supposedly to modernize it and strip out the corruption that had sapped it in the 1990s.

But while Russia made significant headway, Western officials said, a culture of graft and fraud persisted under Mr. Putin that emphasized loyalty above honesty, or even skill. The result was a hodgepodge of elite troops and bedraggled conscripts, advanced tanks and battalions that were powerful only on paper.

“Everyone was stealing and lying. This was a Soviet, and now Russian, tradition,” said Col. Vaidotas Malinionis, a retired Lithuanian commander who served in the Soviet military in the 1980s. Looking at satellite images of the army camp where he served, he said the old barracks and mess hall were still there, with no sign of modernization, and a few buildings had fallen down. “There has been no evolution at all, only regression,” he said.

European, American and Ukrainian officials warned against underestimating Russia, saying it had improved after its muddled invasion of Georgia in 2008. The defense minister overhauled the armed forces, forcibly retired about 40,000 officers and tried to impose more transparency on where money went.

“He made a lot of enemies,” said Dara Massicot, a RAND researcher who studies the Russian military.

Then, in 2012, that minister — in charge of dragging the military out of its post-Soviet dysfunction — became embroiled in a corruption scandal himself. Mr. Putin replaced him with Sergei K. Shoigu, who had no military experience but was seen as someone who could smooth ruffled feathers.

“Russia drew a lot of lessons from the Georgia war and started to rebuild their armed forces, but they built a new Potemkin village,” said Gintaras Bagdonas, the former head of Lithuania’s military intelligence. Much of the modernization drive was “just pokazukha,” he said, using a Russian term for window-dressing.

Contractors like Sergei Khrabrykh, a former Russian Army captain, were recruited into the stagecraft. He said he got a panicked call in 2016 from a deputy defense minister. A delegation of officials was scheduled to tour a training base of one of Russia’s premier tank units, the Kantemirovskaya Tank Division, whose history dates to the victories of World War II.

Billions of rubles had been allocated for the base, Mr. Khrabrykh said, but most of the money was gone and virtually none of the work had been done. He said the minister begged him to transform it into a modern-looking facility before the delegation arrived.

“They needed to be guided around the territory and shown that the Kantemirovskaya Division was the coolest,” Mr. Khrabrykh said. He was given about $1.2 million and a month to do the job.

As he toured the base, Mr. Khrabrykh was stunned by the dilapidation. The Ministry of Defense had hailed the tank division as a unit that would defend Moscow in case of a NATO invasion. But the barracks were unfinished, with debris strewn across the floors, large holes in the ceiling and half-built cinder-block walls, according to photos Mr. Khrabrykh and his colleagues took. A tangle of electrical wires hung from a skinny pole.

“Just about everything was destroyed,” he said.

The interior of a tank base building.

Sergei Khrabrykh

The same base after work was done to cover up its state.

Sergei Khrabrykh

Before the delegation arrived, Mr. Khrabrykh said, he quickly constructed cheap facades and hung banners, covered in pictures of tanks and boasting the army was “stronger and sturdier year by year,” to disguise the worst of the decay. On the tour, he said, the visitors were guided along a careful route through the best-looking part of the base — and kept away from the bathrooms, which had not been repaired.

After the invasion started, the Kantemirovskaya Division pressed into northeastern Ukraine, only to be ravaged by Ukrainian forces. Crews limped away with many of their tanks abandoned or destroyed.

Russian prosecutors have pursued thousands of officers and others for corruption in recent years: One colonel was accused of embezzling money meant for vehicle batteries, another of fraud around mobile kitchens. The deputy chief of the general staff was charged with defrauding the state over radio gear, and a major general sentenced to prison in the case.

In 2019, Russia’s chief military prosecutor said that more than 2,800 officers had been disciplined over corruption violations in the past year alone.

After the invasion, American officials noticed that much of Russia’s equipment was poorly manufactured or in short supply. Tires on wheeled vehicles fell apart, stalling convoys, while soldiers resorted to crowdfunding for clothes, crutches and other basic supplies as the war wore on.

But even more consequential than the corruption, officials and analysts said, were the ways Mr. Putin fundamentally misunderstood his own military.

Russia had, in fact, spent 20 years getting ready for a radically different kind of war.

It had not prepared its military to invade and occupy a country as big and powerful as Ukraine, officials and analysts said. Instead, Russia had largely organized its military to keep U.S. and NATO forces away by inflicting maximum damage from afar.

Central to this strategy was a series of outposts — Kaliningrad by the Baltic, Crimea in the Black Sea, and the Syrian port of Tartus on the Mediterranean — to use long-range missiles to keep Western forces at bay. In the event of conflict, Russia intended to blind the enemy and destroy it from a distance, American officials said.

But in this case, Russia did not crush Ukraine with weeks of missile strikes in advance. It marched in quickly with forces on the ground.

Unlike its more limited campaigns in places like Syria — or the big hypothetical war with NATO it had long planned for — the invasion of Ukraine was simply “not what the Russian military was designed to do,” putting it in a position it was probably “least prepared” to deal with, said Clint Reach, a researcher at RAND.

In other words, the Kremlin picked the “stupidest” of all potential military options by rushing forward and trying to take over Ukraine, said General Budanov, the Ukrainian military intelligence chief.

Russia had not trained its infantry, air and artillery forces to work in concert, move quickly and then do it all again from a new location, officials said. It did not have a clear Plan B after the march on Kyiv failed, and commanders had long been afraid to report bad news to their bosses.

“The collective system of circular, mutual self-deception is the herpes of the Russian Army,” the pro-Russian militia commander Aleksandr Khodakovsky wrote on Telegram in June.

The mounting failures drove a cadre of pro-Russian military bloggers to a boiling point. While still cheerleaders for the war, they began to openly criticize Russia’s performance.

“I’ve been keeping quiet for a long time,” the blogger Yuri Podolyaka said in May, after hundreds of soldiers died in a river crossing. “Due to stupidity — I emphasize, because of the stupidity of the Russian command — at least one battalion tactical group was burned, possibly two.”

A Ukrainian soldier atop an abandoned Russian tank at a river crossing where hundreds of Russian soldiers died.

Ivor Prickett for The New York Times

The fury eventually reached Mr. Putin himself. On the sidelines of his marquee annual economic conference in St. Petersburg in June, the president held a meeting that had become a tradition: a sit-down with news media chiefs. This time, though, the bloggers were the headline guests.

Mr. Putin sat alone at one end in a cavernous hall, according to one attendee, who provided a photo of the private gathering. Some of the bloggers took the floor and peppered Mr. Putin with messages and complaints from the front.

“It became a very concrete conversation, a surprising one for us,” the person present said. “We’d never had such conversations.”

It appeared to the person there that Russia’s intelligence agencies were using the bloggers to shift the blame for the war’s failings to the Ministry of Defense. Mr. Zatulin, the Putin ally in Parliament, insisted he supported the war, but said a blame game has broken out, and took a side himself.

“Of course, to a certain degree, we now have an element of everyone wanting to dump the responsibility on someone else,” Mr. Zatulin said.

“But I think that the main miscalculations,” he added, “were made by the Defense Ministry and the General Staff” — the military’s top brass.

His mission seemed clear enough. With his marksman’s rifle, bundle of papers and copies of his Russian passport in his pack, Ruslan was one of thousands of poorly trained, underequipped men asked to defend a huge swath of territory that Russia had seized in northeastern Ukraine.

By summer’s end, Russian leaders had sent their best troops far to the south, leaving skeleton crews behind. So when the Ukrainians swept in and attacked the northeast, hoping to recapture occupied land, soldiers like Ruslan were cut down or melted away in a chaotic retreat.

Military analysts had warned of such a danger before the invasion. Even as tens of thousands of Russian soldiers massed ominously along Ukraine’s borders, they said, the Kremlin had not sent enough to occupy the entire country. The Russian war plans for the 26th Tank Regiment signaled the same problem: Expect no reinforcements.

Russia managed to take territory, frequently at enormous cost. But how to keep it was often an afterthought.

“The army, the generals, the soldiers weren’t ready,” said Mr. Tsaryov, the man American officials identified as a puppet leader the Kremlin could install in Ukraine.

A kindergarten classroom near Izium was used as a base by retreating Russian soldiers and emblazoned with the military symbol “Z” in September.

Nicole Tung for The New York Times

He said the Russian Army had spread itself so thin across Ukraine after invading that it “would move through cities and not leave behind even a garrison, even a small one to stick up a Russian flag and defend it.”

In the northeastern region of Kharkiv, Russian commanders put men like Ruslan at roadblocks and moved on.

He had little else besides the printouts in his pack, which Ukrainian soldiers recovered with what they believe to be his body in September. The rifle next to him suggested he was a sniper. But while snipers in modern militaries often go through weeks of additional special training, Ruslan’s teacher appeared to be the internet.

“Hello dear soldier!” read the unsigned letter in his pack. “You have to risk your life so that we can live peacefully. Thanks to you and your comrades our army remains so strong, mighty and can protect us from any enemy.”

More than 50 pages of Russian documents, collected from three towns in the Kharkiv region and reviewed by The Times, show a timeless truth: Foot soldiers bear the outsize burden of combat.

The documents — shared with three independent military experts, who considered them credible — detail how Russia relied on bedraggled backup forces, many of them separatist fighters from Ukraine’s long conflict in its divided east, to hold territory as the regular Russian Army fought hundreds of miles away.

The 202nd Rifle Regiment of the Luhansk People’s Republic — Kremlin-backed separatists in eastern Ukraine — was one of them. It had nearly 2,000 men, but was almost completely dependent on foot soldiers.

More than a dozen pages of its rosters detail the particulars of the unit’s suffering, down to a lack of warm clothing and boots.

Several of its soldiers were in their 50s, including one who experienced “cardiac failure,” while one of its youngest casualties, a 20-year-old named Vladimir, endured “frostbite of the lower limbs.” Yet another complained on a phone call intercepted by the Ukrainians that he had no armored vest and a helmet from the 1940s.

“Our battalion, for instance, has already gone more than three weeks without receiving ammunition from the army,” the pro-Russian militia commander, Mr. Khodakovsky, said on Telegram in September.

In an interview, another soldier described having only the vaguest sense of how to use his weapon.

He recounted being advised to fire judiciously, one round at a time, rather than blasting his rifle uncontrollably. But he wasn’t sure how to do that. So, shortly before going into combat, he said, he turned to a commander and asked how to switch his rifle off fully automatic.

Russia came to rely on such battered, inexperienced troops after months of tactics that more closely resembled 1917 than 2022. Commanders sent waves of troops into the range of heavy artillery, eking out a few yards of territory at grievous tolls.

When one Russian unit arrived in eastern Ukraine, it was quickly whittled down to a haggard few, according to one of its soldiers.

During fighting in the spring, he said, his commanders ordered an offensive, promising artillery to support the attack. It never came, he said, and his unit was devastated.

Yet commanders sent them right back into the melee all the same.

“How much time has passed now? Nine months, I think?” he said. “In this whole time, nothing has changed. They have not learned. They have not drawn any conclusions from their mistakes.”

He recounted another battle in which commanders sent soldiers down the same path to the front, over and over. On each trip, he said, bodies fell around him. Finally, after being ordered to go a fifth time, he and his unit refused to go, he said.

In all, he said, his unit lost about 70 percent of its soldiers to death and injury, ruining any faith he had in his commanders.

“Nobody is going to stay alive,” he said. “One way or another, one weapon or another is going to kill you.”

American officials realized early on that they had vastly overestimated Russia’s military. The morale of rank-and-file soldiers was so low, the Americans said, that Russia began moving its generals to the front lines to shore it up.

But the generals made a deadly mistake: They positioned themselves near antennas and communications arrays, making them easy to find, the Americans said.

Ukraine started killing Russian generals, yet the risky Russian visits to the front lines continued. Finally, in late April, the Russian chief of the general staff, Gen. Valery Gerasimov, made secret plans to go himself.

American officials said they found out, but kept the information from the Ukrainians, worried they would strike. Killing General Gerasimov could sharply escalate the conflict, officials said, and while the Americans were committed to helping Ukraine, they didn’t want to set off a war between the United States and Russia.

The Ukrainians learned of the general’s plans anyway, putting the Americans in a bind. After checking with the White House, senior American officials asked the Ukrainians to call off the attack.

“We told them not to do it,” a senior American official said. “We were like, ‘Hey, that’s too much.’”

The message arrived too late. Ukrainian military officials told the Americans that they had already launched their attack on the general’s position.

Dozens of Russians were killed in the strike, officials said. General Gerasimov wasn’t one of them.

Russian military leaders scaled back their visits to the front after that.

More than 20 years into a murder sentence, Yevgeny Nuzhin saw his chance at salvation swoop in by helicopter.

Mr. Prigozhin — the close confidant of Mr. Putin, known for stirring up trouble across the Middle East and Africa with his mercenary army, Wagner — came to Mr. Nuzhin’s prison south of Moscow in August, looking for recruits.

Heaving with patriotic fervor, Mr. Prigozhin gave the kind of speech he has delivered at other Russian prisons in recent months, some shared online. In one, also from August, Mr. Prigozhin, dressed in a drab beige uniform, promised pardons for the inmates who made it back from Ukraine alive. Those who didn’t, he said, would “be buried in the alleys of the heroes.”

He also issued a warning: Anyone thinking of deserting his forces once in Ukraine, he said in the video, would be shot.

Mr. Nuzhin accepted Mr. Prigozhin’s offer, but ignored the warning.

After two days at the front, where he spent his time collecting the bodies of dead Wagner soldiers, he used the cover of darkness to slip away and surrender to Ukrainian troops.

“What good has Putin done in the time that he has been in power? Has he done anything good?” Mr. Nuzhin told The Times after being taken into Ukrainian custody. “I think this war is Putin’s grave.”

Yevgeny Nuzhin, 55, a Russian prisoner of war held by Ukraine, in October.

Brendan Hoffman for The New York Times

Mr. Putin’s reliance on mercenaries and convicts is one of the more unusual features of his war in Ukraine. Mr. Prigozhin is just one of a handful of strongmen active in the war, all of them managed by Mr. Putin, who has carved up the administration of much of Russia into competing fiefs run by people loyal to him above all.

Beyond the mercenaries controlled by Mr. Prigozhin, who rose to prominence as a caterer of Kremlin events, there is also the Russian national guard, overseen by Mr. Putin’s former bodyguard. And there is the unit commanded by the Chechen leader, Mr. Kadyrov — whose fighters were found and attacked because of their misadventures on TikTok.

As far as officials can tell, the Russian military has limited coordination with any of them.

“There was no unified command, there was no single headquarters, there was no single concept and there was no unified planning of actions and command,” said General Ivashov, the retired Russian officer who warned the war would go badly. “It was destined to be a defeat.”

The splintered Russian forces have sparred openly. After Russian forces withdrew from northeast Ukraine in late summer, Mr. Kadyrov called for the Russian commander responsible to be demoted to private and shipped to the front, “to wash his shame away with blood.”

Mr. Prigozhin weighed in, too: “All these bastards should go with machine guns barefoot to the front.”

The public finger-pointing has added to a sense of disarray within the Russian war effort. Mr. Putin has replaced several top military commanders. Yet he has stuck with Mr. Shoigu, his defense minister, and with General Gerasimov, the chief of the military’s general staff, because firing them would amount to a public acknowledgment that the war is going badly, an admission Mr. Putin is loath to make, argued General Budanov, the Ukrainian military intelligence chief.

“They are still trying to maintain the illusion that everything is going well,” he said.

The friction has, at times, run all the way down to the troops in the battle zone.

After a battlefield argument in the Zaporizhzhia region over the summer, a Russian tank commander drove his T-90 tank not at the enemy but toward a group of Russian national guard troops, firing at their checkpoint and blowing it up, said Fidar Khubaev, describing himself as а Russian drone operator who witnessed the episode.

“Those types of things happen there,” said Mr. Khubaev, adding that he fled Russia in the fall.

Of all the supplementary armies charging into Ukraine, Mr. Prigozhin’s Wagner has become especially pivotal. Its troops have received glowing coverage on Russian state television, and in November they were profiled in a documentary film called “Wagner: Contract with the Motherland” produced by RT, one of the Kremlin’s primary propaganda outlets.

“Until recently, Wagner has been one of the most closed and secretive organizations, but for us they have made a huge exception,” Andrey Yashchenko, the film’s presenter, says in the opening montage, which shows tanks rolling through rubble-strewn villages.

In the first five months of the war, there was almost no public mention of Wagner or Mr. Prigozhin’s involvement in Ukraine. By late summer, as the Russian military began to collapse under Ukrainian campaigns in the northeast and south, Mr. Prigozhin stepped into the spotlight.

After years of denying any links to Wagner — and sometimes its very existence — Mr. Prigozhin suddenly went public, making a show of visiting his troops in Ukraine, handing out medals, attending funerals and trumpeting his independence on the battlefield.

“Wagner almost always fights alone,” he said in an Oct. 14 post on the page of his catering company on VK, a Russian social media site.

A Times analysis of videos in Ukraine found that Wagner troops are often showcasing some of Russia’s most advanced weaponry, including tanks, fighter aircraft and thermobaric rocket launchers. And because of his connection with the president, Mr. Prigozhin is given priority over other military units for arms and equipment, a senior European official said.

Mr. Peskov, the Kremlin spokesman, denied that Russia’s separate fighting forces were causing confusion or division, insisting they all report to Russia’s top military brass. The prominence of Mr. Prigozhin and Mr. Kadyrov, he said, was merely a function of their public-relations efforts.

“Some people are more active in the information space, some people are less active,” Mr. Peskov said. “But it doesn’t signify any, let’s say, independence.”

Despite its weaponry and bravado, Wagner has struggled on the battlefield. Some Ukrainian soldiers say it is a formidable foe. Yet for nearly six months, Wagner’s troops have been trying to seize the small industrial city of Bakhmut, in the eastern Donetsk region, and have been kept at bay by Ukrainian forces at great cost to both sides — prompting a rare public acknowledgment of Ukraine’s fighting prowess.

The frontline city of Bakhmut, where Wagner forces have fought for months.

Tyler Hicks/The New York Times

“The situation is difficult but stable,” Mr. Prigozhin said in the Oct. 14 post. “The Ukrainians are offering dignified resistance. The legend about Ukrainians running away is just that, a legend. Ukrainians are guys with steel balls just like us. This isn’t a bad thing. As Slavs, we should take pride in this.”

Hundreds of Wagner troops have been killed in the war, and several of the group’s fighter jets have been downed. The convicts Mr. Prigozhin has recruited appear to be little more than cannon fodder and make up a vast majority of casualties among Wagner forces, according to an assessment by Ukraine’s military intelligence agency, which said in October that about 8,000 Wagner troops were fighting in Ukraine.

Another former Russian inmate recruited by Mr. Prigozhin said he was left in a shallow trench at the front lines near Bakhmut for four days with no food or water and little sense of what he was supposed to be doing, other than dragging away the many bodies of his dead comrades.

It was no wonder, he said, that some of Wagner’s recruits decided to flee.

To keep control, Mr. Prigozhin has resorted to extreme punishment, showing how the war has whittled away the vestiges of rule of law in Russia.

Like Mr. Putin, whose spies have been accused of poisoning and assassinating perceived traitors all over the world, Mr. Prigozhin has said that treachery is the worst sin any Russian can commit. He has proposed setting up his own Gestapo-like police force to hunt down the disloyal, including, he has said, Russian businessmen “who leave our country in their business jets.”

The fate of Mr. Nuzhin serves as a grisly warning.

Mindful of the pressures on prisoners of war and the risks they face, The Times has chosen to withhold their names. And, as with the other people we interviewed, we use documents and other evidence to vet their claims.

In Mr. Nuzhin’s case, we did not publish our interview with him, but he also spoke to Ukrainian media, which broadcast portions of his account. Soon after, he was released in a prisoner swap — and ended up back in the hands of Wagner.

He then appeared in a video on a pro-Russian Telegram account. In it, Mr. Nuzhin’s head was taped to a block. Looming over him was a man in camouflage, holding a sledgehammer.

“I woke up in this basement, where I was told that I will be judged,” Mr. Nuzhin says in the video, his voice dry and gravelly. The sledgehammer then swings down and crushes his skull.

Shortly after, Mr. Prigozhin released a statement endorsing Mr. Nuzhin’s murder.

“Nuzhin betrayed his people, betrayed his comrades, betrayed them consciously,” the statement said. “He planned his escape. Nuzhin is a traitor.”

A day later, asked about the video on a conference call with journalists, Mr. Peskov said, “It’s not our business.”

The resignation exists in Moscow, too, where opposition to the war is common, but rarely expressed above whispers.

“We’re giving each other looks, but to say something is impossible,” one former Putin confidant in Moscow said, describing the atmosphere in the halls of power.

A priest blessing men conscripted into the Russian forces in Moscow in October.

Nanna Heitmann for The New York Times

Mr. Tinkov, the former tycoon who founded one of Russia’s biggest banks, posted on Instagram in April that the war was “crazy” and excoriated Mr. Putin in an interview with The Times, thinking he’d set the stage for more of Russia’s powerful to follow suit.

“Why didn’t anyone speak out after me?” Mr. Tinkov lamented.

One prominent Russian public figure who privately described the war as a “catastrophe” explained his silence by quoting the Soviet poet Yevgeny Yevtushenko.

In the day of Galileo, one of his poems says, another scientist was also “well aware the earth revolved” around the sun, but he “had a large family to feed.”

By keeping Russia’s borders open, despite calls from hard-liners to shut them, Mr. Putin has allowed Russians unhappiest with the war — who might have otherwise protested — to leave the country. And the West’s wide-ranging sanctions have not turned the elite against Mr. Putin, at least not publicly.

“In textbooks, they call this political terrorism,” said Mr. Melnichenko, the coal and fertilizer billionaire. “To say anything at gunpoint, even if you want to say it — it’s better not to.”

Mr. Melnichenko has been penalized — unfairly, he insists — for the Russian invasion. The Italians said they seized his 468-foot sailboat featuring an underwater observation pod in the keel, and sanctions forced him to abandon his longtime home in Switzerland. He now holds court on white couches in the lobby of a luxury hotel in Dubai.

Mr. Melnichenko offered some veiled criticism of the invasion, declaring that “any war is horrible — the faster it ends, the better.” But he insisted he was powerless to do anything to hasten its end, and that any further opinions “would trigger immediate risks.”

Despite the sanctions, Mr. Putin sees himself on a far grander timeline than the election cycles and shifting political winds steering Western leaders, who come and go, those who know him say. In June, he compared himself to Peter the Great as a leader “returning” and “strengthening” Russian lands.

When the 18th-century czar founded St. Petersburg, Mr. Putin said, the Europeans did not consider that territory to be Russian — suggesting that Mr. Putin expects the West to someday come around and recognize his conquests as well.

In late November, at his suburban Moscow residence, Mr. Putin met with mothers of Russian soldiers. It was a distant echo of one of the lowest moments of his tenure: his encounter with the families of sailors aboard a sunken submarine in 2000, when a crying woman in a remote Arctic town demanded, “Where is my son?”

Twenty-two years later, the Kremlin was careful to prevent such outpourings of grief. Around a long table with individual teapots for the handpicked women — some of them state employees and pro-Kremlin activists — Mr. Putin showed no remorse for sending Russians to their deaths.

After all, he told one woman who said her son was killed in Ukraine, tens of thousands of Russians die each year from car accidents and alcohol abuse. Rather than drinking himself to death, he told her, her son died with a purpose.

“Some people, are they even living or not living? It’s unclear. And how they die, from vodka or something else, it’s also unclear,” Mr. Putin said. “But your son lived, you understand? He reached his goal.”

He told another mother that her son was not only fighting “neo-Nazis” in Ukraine, but also correcting the mistakes after the collapse of the Soviet Union, when Russia “enthusiastically indulged in the fact” that the West was “trying to control us.”

“They have a different cultural code,” he told her. “They count the genders there by the dozens.”

It was a stark display of Mr. Putin’s preoccupations and revanchist politics. But several people who have known him for decades rejected any notion that he had grown irrational.

“He’s not crazy and he’s not sick,” a person who has known Mr. Putin since the 1990s said. “He’s an absolute dictator who made a wrong decision — a smart dictator who made a wrong decision.”

Mr. Putin has shown few hints that he’s willing to turn back now. Last month, the C.I.A. director, Mr. Burns, met for the first time since the invasion with Sergei Naryshkin, the director of the Foreign Intelligence Service of Russia. The meeting, at the headquarters of Turkish intelligence in Ankara, took place to reopen a direct, in-person line of communication between Washington and Moscow, but the tone was not one of reconciliation.

According to senior officials present, Mr. Naryshkin said Russia would never give up, no matter how many troops it lost on the battlefield. This month, Ukrainian leaders warned that Russia might be massing troops and arms to launch a new offensive by spring.

The world has been debating Mr. Putin’s willingness to use a nuclear weapon in Ukraine. People who know him don’t discount the possibility, but they also believe he expects to defeat the West and Ukraine in a long-term, non-nuclear test of wills.

As one senior NATO intelligence official put it, Russian generals “acknowledge the incompetence, lack of coordination, lack of training. They all recognize these problems.” Still, they seem confident of an “eventual victory” because, the official said, “Putin believes this is a game of chicken between him and the West, and he believes the West will blink first.”

Mr. Putin has already shown a talent for the long game, agreed Mr. Tinkov, the banking magnate who turned against the Kremlin, noting how the Russian leader had spent decades bringing Russia’s elite to heel.

“He slowly outplayed everyone, because the thing was: It was like he had unlimited time,” Mr. Tinkov said. “He is still behaving in this war as though he has an unlimited amount of time — as though he plans to live for 200 years.”

Domestically, the pressure on Mr. Putin has been fairly muted. For all the losses his army has endured, there have been no significant uprisings among Russian troops. Even the newly drafted continue to go without serious protest.

Aleksandr, the soldier drafted into the 155th, is still enraged at the way he and his comrades were dropped into Ukraine with few bullets for their aging rifles and forced to live in a cowshed with only a few meal packets to share. His commanders flat-out lied, he said, telling them they were going for additional training — when in fact they were sent to the front lines, where most were killed or grievously wounded.

After months of fighting, Russia announced last month that it had finally captured Pavlivka, but soldiers said it came at tremendous cost.

Aleksandr had been drafted in September along with three close childhood friends, he said. He and another suffered concussions. One lost both legs. The fourth is missing.

But when he is discharged from the hospital, he said, he fully expects to return to Ukraine, and would do so willingly.

“This is how we are raised,” he said. “We grew up in our country understanding that it doesn’t matter how our country treats us. Maybe this is bad. Maybe this is good. Maybe there are things we do not like about our government.”

But, he added, “when a situation like this arises, we get up and go.”

A burning oil depot that local residents said had been hit by a Russian mortar barrage in Kherson.

Finbarr O’Reilly for The New York Times