During the war with Ukraine, the number of billionaires in Russia has reached an all-time high. But in the 25 years Vladimir Putin has been in power, Russia's rich and powerful - known as oligarchs - have lost almost all their political influence.

All this is good news for the Russian president. Western sanctions have failed to turn the uber-rich into his opponents, and his carrot-and-stick policies have turned them into silent backers.

Former banking billionaire Oleg Tinkov knows exactly how the sticks work.

The day after he criticised the war as "crazy" in an Instagram post, his executives were contacted by the Kremlin. They were told his Tinkoff Bank, Russia's second-largest at the time, would be nationalised unless all ties to its founder were cut.

"I couldn't discuss the price," Tinkov told the New York Times. "It was like a hostage - you take what you are offered. I couldn't negotiate."

Within a week, a company linked to Vladimir Potanin, currently Russia's fifth-richest businessman, who supplies nickel for fighter jet engines, announced it was buying the bank. It was sold for only 3% of its true value, says Tinkov.

In the end, Tinkov lost almost $9bn (£6.5bn) of the fortune he once had and left Russia.

This is a far cry from the way things were before Putin became president.

In the years following the breakup of the Soviet Union, some Russians became fabulously wealthy by taking ownership of massive state-owned enterprises and exploiting the opportunities of their country's nascent capitalism.

Their newly acquired wealth brought them influence and power during a period of political turmoil, and they became known as oligarchs.

Russia's most powerful oligarch, Boris Berezovsky, claimed to have orchestrated Putin's ascent to the presidency in 2000. Years later, he appealed for forgiveness for doing so: "I didn't see the future greedy tyrant and usurper in him, the man who would trample freedom and stop Russia's development," he wrote in 2012.

Berezovsky may have exaggerated his role, but Russia's oligarchs were certainly capable of pulling strings at the highest echelons of power.

A little more than a year after his apology, Berezovsky was found dead in mysterious circumstances in exile in the UK. By that time, the Russian oligarchy was well and truly dead, too.

So when Putin gathered Russia's richest in the Kremlin hours after ordering the full-scale invasion of Ukraine on 24 February 2022, there was little they could do to object, even though they knew their fortunes were about to take a massive hit.

"I hope that in these new conditions, we'll work together just as well and no less effectively," he told them.

One reporter present at the meeting described the assembled billionaires as "pale and sleep-deprived".

The run-up to the invasion was very bad for Russia's billionaires, and so was its immediate aftermath.

According to Forbes magazine, their number fell from 117 to 83 between April 2021 and April 2022 due to the war, sanctions, and a weakened rouble. Collectively, they lost $263bn - or 27% of their wealth each on average.

But the years that followed showed that immense benefits were to be reaped from being part of Putin's war economy.

Lavish spending on the war spurred Russia's economic growth of more than 4% a year in 2023 and 2024. It was good for even those among Russia's ultra-rich who were not making billions directly out of defence contracts.

In 2024, more than half of Russia's billionaires either played some role in supplying the military or benefited from the invasion, says Giacomo Tognini, from Forbes's Wealth team.

"That's not even counting those who aren't directly involved, but do need a relationship of sorts with the Kremlin. And I think it's fair to say that anyone running a business in Russia needs to have a relationship with the government," he told the BBC.

This year saw the highest ever number of billionaires in Russia - 140 - on the Forbes list. Their collective worth ($580bn) was just $3bn shy of the all-time high registered in the year before the invasion.

While allowing loyalists to profit, Putin has consistently punished those who have refused to toe the line.

Russians remember all too well what happened to oil tycoon Mikhail Khodorkovsky. Once Russia's richest man, he spent 10 years in jail after launching a pro-democracy organisation in 2001.

Since the invasion, almost all of Russia's mega-rich have stayed quiet, and those few who have publicly opposed it have had to abandon their country and much of their wealth.

Russia's wealthiest are clearly key to Putin's war effort, and many of them, including the 37 business people summoned to the Kremlin on 24 February 2022, have been targeted by Western sanctions.

But if the West wanted to make them poorer and turn against the Kremlin, it has failed, given the continuing wealth and absence of dissent among Russian billionaires.

If any of them had considered defecting to the West with their billions, the sanctions made that impossible.

"The West did everything possible to ensure that Russian billionaires rallied around the flag," says Alexander Kolyandr of the Center for European Policy Analysis (CEPA).

"There was absolutely no plan, no idea, no clear path for any of them to jump ship. Assets were sanctioned, accounts frozen, and property seized. All that effectively helped Putin to mobilise the billionaires, their assets and their money, and use it to support the Russian war economy," he tells the BBC.

The exodus of foreign companies in the wake of the invasion of Ukraine created a vacuum quickly filled by Kremlin-friendly businesspeople who were allowed to buy up highly lucrative assets on the cheap.

This created a new "army of influential and active loyalists", argues Alexandra Prokopenko of the Carnegie Russia Eurasia Center.

"Their future well-being depends on continued confrontation between Russia and the West," while their worst fear is the return of the previous owner, she says.

In 2024 alone, 11 new billionaires emerged in Russia in this way, according to Giacomo Tognini.

Russia's leader has maintained a firm grip on the country's key movers and shakers, despite the war and Western sanctions - and in some respects because of them.