Most people who know Milner have shrugged off his connection to a pro-Putin oligarch. Milner’s business – early-stage tech investing – is far removed from the world of the Russian oligarchs who got rich by acquiring state assets at dirt-cheap prices. And the money from Usmanov, as well as from Russia’s state-controlled VTB Bank, came during the presidency of Dmitry Medvedev, when the Obama administration in the United States was urging a “reset” of Russian-American relations.

But now, as Putin’s army is shelling Ukrainian cities, Usmanov and VTB are on sanction lists. And Milner is on the defensive. “I cannot go back and change history,” he says during several hours of Zoom interviews. “I cannot change the fact I was born in Russia. I cannot change the fact we had some Russian funds.”

Milner’s non-profit Breakthrough Prize Foundation and his venture capital firm, DST Global, have both released statements condemning “Russia’s war against Ukraine, its sovereign neighbour”, as DST puts it. A Breakthrough Prize Foundation statement, credited to chairman Pete Worden, referred to Russia’s “unprovoked and brutal assaults against the civilian population”. Milner and his organisations have pledged US$14.5 million to fund humanitarian efforts.

Even so, Milner himself is careful when speaking about the war in Ukraine. He declines to express an opinion on Putin, instead citing the statements made by his organisations, and calls the war a “heartbreaking tragedy”.

Now 60, he holds up a black-and-white family photograph, taken around 1970. It shows him as a boy, wearing a knit hat, in Zaporizhzhya, Ukraine, where he says he spent many summers with his father’s family. Days earlier, he says, he and a cousin helped evacuate a family friend, an elderly woman, from Cherkasy; her husband had decided not to leave.

“I fully stand behind statements made by DST Global and the Breakthrough Prize Foundation,” he says.

Milner, whose net worth is US$3.9 billion, according to the Bloomberg Billionaires Index, is navigating a precarious situation. There is a long history of foreign cash of dubious origin finding its way into Silicon Valley – most notably the funds from Saudi Arabia that continued to flow even after the dissident journalist Jamal Khashoggi was murdered by government agents.

But the war in Ukraine has galvanised the West, says Ayako Yasuda, a finance professor at the University of California, Davis, in the US. “Start-ups do have real reasons to worry about receiving funding from DST,” she says.

There is a risk that Milner could be tainted by the association, causing entrepreneurs to skip those lavish parties and turn down funding offers from DST. Investors might also hesitate to recommit to the firm when it next raises funds, and Milner’s philanthropic work, most notably a series of rich awards for scientific achievement known as the Breakthrough Prize, could lose its cachet. Milner plays down those risks.

“Facts are on our side,” he says, arguing that DST has long been independent of Kremlin interests. He spoke from Dubai, where he was helping to raise funds for a company he declines to name.

He is still a Russian citizen but also holds Israeli citizenship. He has been living in the US on an O-1 visa, for people of “extraordinary ability”, a common path for foreign-born tech entre­preneurs. He paid US$100 million for the estate in Los Altos in 2011 and considers the US his home.

If Milner is frustrated, it is partly because his move to the US was made during a years-long campaign to separate himself from his controversial early backers. DST, he says, hasn’t taken any money from Russia since 2011, when it raised a US$900 million fund, nor has it made any investments in Russia.

Milner notes that, until recently, most Western banks were doing business with Russia, years after he had stopped. He says he hasn’t seen Usmanov in about five years and hasn’t been to Russia in eight.

To support his claim about separating himself from Kremlin-connected cash, he shares a letter dated March 19 from his chief financial officer, Kenneth Leung, that outlines the steps DST takes to comply with “know your customer” and anti-money-laundering provisions. “If he lies,” Milner deadpans, referring to Leung, “he will go to prison.”

The firm is actively working on a handful of deals in various stages of diligence, he says. Having raised a ninth fund of almost US$4 billion in 2021, DST won’t need to raise funds again for a year or two, and Milner says he thinks investors will stay loyal. Some left DST in recent years, but it wasn’t because of politics, he says. It was because in 2018 he raised his fees to 25 per cent of profits, up from 20 per cent.

Milner has powerful defenders. “Yuri Milner has been a valued friend and partner to me, our firm, and many of the US’ best new technology companies for nearly two decades,” Marc Andreessen, a board member of Meta Platforms (aka Facebook), wrote in a tweet in the first week of March.

Max Levchin, the Ukrainian-born CEO of the financial technology company Affirm Holdings, calls Milner a good friend. “He has been a visionary investor, and equally importantly, a passionate supporter and promoter of real science,” Levchin said in a statement.

Ryan Petersen, CEO of freight giant Flexport, has taken a series of investments from DST, the most recent in February, and says he wouldn’t hesitate to accept more. “I have zero concerns,” he says, adding that any questions he had about DST’s investors were fully satisfied years ago. “Yuri has incredibly high ethics.”

He calls efforts to connect Milner to the Kremlin “on some level a little crazy” and suggests that they are discriminatory, conflating Milner’s birthplace with Putin’s policies.

Milner’s status comes from his success as an early-stage investor and from his interest in science. Named after the great cosmonaut Yuri Gagarin, Milner has a degree in physics from Moscow State University.

After deciding he would never rise to the top of the field, he dropped out of a physics PhD programme and started selling computers. In the late 1980s, as the Soviet Union collapsed, he moved to the US to study business at the University of Pennsylvania’s Wharton School.

Milner worked at the World Bank in Washington in the early 90s and then moved back to Russia to run a brokerage. Inspired by a report by famed internet analyst Mary Meeker, he launched an incubator and investment fund to develop Russian internet companies in the mould of eBay and Amazon. He founded Digital Sky Technologies, a precursor venture capital firm, in 2005, just as valuations were recovering from the 2000 dotcom crash.

By the late 2000s, Milner, looking to diversify beyond Russia, created DST Global and set his sights on Facebook. When DST first invested in Facebook, in 2009, it was at a US$10 billion valuation, a huge price for a young company during the middle of a recession. But almost overnight, the US$200 million investment, which included more Usmanov-connected funds than previously disclosed, according to a 2017 New York Times report drawing on leaked documents known as the Paradise Papers, established DST as one of the top venture capital firms in Silicon Valley.

As his fortune grew, Milner spent lavishly on his personal life. He also put up more than US$75 million to fund a search for extraterrestrial life and dropped US$300 million on the Breakthrough Prizes. In 2013, he invested in satellite company Planet Labs and in Elon Musk’s rocket company SpaceX. Milner says the investment in SpaceX was about US$10 million. He sold his position two years later for US$23.56 million.

The SpaceX deal is one that hasn’t been previously reported. Around the same time, the company, a major Pentagon contractor, was bragging publicly that its rockets did not use Russian components, unlike others in the space industry.

In April 2014, the company sued the US Air Force for the right to compete for contracts, complaining that existing agreements were funnelling money to Russia’s defence industry, including to sanctioned Russians. Milner says he was under no pressure to divest and sold his stake only because he didn’t appreciate the full potential of the satellite market.

“I underestimated SpaceX,” he says. “Divesting early was a mistake.” He says he admires Musk and has talked with him about topics such as looking for aliens and travelling to the stars. Representatives for SpaceX did not respond to requests for comment.

Besides Breakthrough Listen, which searches for communication from aliens, Milner has also funded Breakthrough Starshot, which is in the early stages of a decades-long project to build tiny and ultra-fast spacecraft that would fly to our neighbouring star system, Alpha Centauri.

He says the war in Ukraine throws the purpose of the projects, outlined in a treatise he published in 2021 called the “Eureka Manifesto”, into sharper focus. If we learn that life does exist beyond Earth, the discovery could “be the unifying moment for our civilisation”, he says. “It can be our generation’s equivalent to the first step on the moon. One of those moments when we all feel as one.”

He says he is confident that life beyond Earth would demonstrate that our current distinctions based on national borders hold us back. “If there’s a civilisation out there that’s a million or a billion years ahead of us, I’m very confident that it came together as one,” he says.

Milner, in other words, is a lot more forthcoming on hypothetical intergalactic political questions than he is on questions about Vladimir Putin.