Former US President Joe Biden has given his first in-depth interview since he left the White House in January, speaking to the BBC about his legacy, foreign policy and his view of President Donald Trump’s first 100 days.

He said that he had few regrets, but he offered grave warnings about global affairs as Europe marks 80 years since the end of World War Two on the continent.

Biden spent much of his time in public office – as a senator, vice-president and president – focusing on US foreign policy, and it remains a top concern.

The former president also reflected on his decision to drop out of the 2024 election race – but he had less to say about any mistakes he and the Democrats may have made along the way.

Here are five key takeaways from his interview with Nick Robinson for BBC Radio 4’s Today programme.

Biden’s ill-fated decision to seek a second presidential term may haunt Democrats for a generation. Three months removed from power, however, the former president said he didn’t think “it would have mattered” if he had abandoned his re-election ambitions earlier, before a disastrous debate forced his hand in July 2024.

Kamala Harris, who became the nominee after Biden dropped out just four months before the election, was a “good candidate” who was “fully funded”, he said.

Democratic strategists have lamented that the last-minute handover left their campaign flat-footed, ultimately aiding Trump’s path to the White House, even as Democrats held a financial advantage in the 2024 race.

Biden boasted of being “so successful on our agenda” – a reference to the major legislation enacted in his first two years in office on the environment, infrastructure and social spending, as well as the better-than-expected Democratic performance in the 2022 midterm elections.

“It was hard to say now I’m going to stop,” he said. “Things moved so quickly that it made it difficult to walk away.”

Ultimately, quitting was “the right decision”, he said, but it was “just a difficult decision”.

Biden described the Trump administration’s suggestion that Ukraine give up territory as part of a peace deal with Russia as “modern-day appeasement” – a reference to European allies that allowed Adolf Hitler to annex Czechoslovakia in the 1930s in an ill-fated attempt to prevent a continent-wide conflict.

“I just don’t understand how people think that if we allow a dictator, a thug, to decide he’s going to take significant portions of land that aren’t his, that that’s going to satisfy him. I don’t quite understand,” Biden said of Russian President Vladimir Putin.

The term “appeasement” gets kicked around a lot in American politics, and the list of foreign leaders compared with modern-day “Hitlers” is a long one.

Though Biden’s repeated assertion that Russian tanks would be rolling through central Europe if America and its allies didn’t support Ukraine is impossible to prove, he views the threat posed by Putin as serious and worthy of the comparison.

Biden also said that if the US allowed a peace deal that favoured Russia, Putin’s neighbours would be under economic, military and political pressure to accommodate Moscow’s will in other ways. In his view, the promise of American support to European allies becomes less believable and less of a deterrent.

Under Biden, the US helped expand the Nato to include Finland and Sweden – one of the former president’s signature foreign policy achievements. Now, he says Trump is turning his back on America’s European allies and threatening the very foundations of Nato and its mutual defence agreement.

The former president described the thought of Nato breaking apart as a “grave concern”. Already, he warned, US allies were doubting American leadership.

“I think it would change the modern history of the world if that occurs,” he said. “We are not the essential nation, but we are the only nation in position to have the capacity to bring people together to lead the world.”

There are some in Trump’s circle – perhaps including the president himself – who believe that a more restrained America, less concerned with global security and more focused on regional self-sufficiency, is best way to ensure long-term prosperity in a world of competing global powers. They argue that America’s post-Cold War dominance was a historical anomaly.

Biden, whose political career spans those decades of American supremacy, disagrees.

In his interview, Biden sounded like most modern American presidents before him. He used words like freedom, democracy and opportunity to describe American principles.

But in Biden’s view, those principles also include a sense of decorum, especially towards long-standing allies.

He said Trump’s February meeting-turned-argument with Ukrainian President Volodymyr Zelensky in the Oval Office was “sort of beneath America”. He argued Trump’s territorial designs on Canada, Greenland and the Panama Canal were “not who we are”.

“What president ever talks like that? That’s not who we are. We’re about freedom, democracy, opportunity, not about confiscation,” he said.

When asked about Trump’s first 100 days in office – which included dramatic attempts to expand presidential power – Biden said he would let history judge his successor, but “I don’t see anything that’s triumphant”.

It was the kind of understatement that surely will irk some on the left. Since the start of Trump’s second term, rank-and-file Democrats have been clamouring for their party to do more to resist the president’s agenda.

Biden said he didn’t think Trump would succeed in flouting courts or the law, or diminishing congressional power, in part because the president’s fellow Republicans are “waking up to what Trump is about”.

“I don’t think he’ll succeed in that effort,” he said.

The idea that members of Trump’s own party will turn on him is a recurring one for Biden. In 2019, he predicted there would be an “epiphany” among Republicans once Trump was out of the White House, ushering in a new era of bipartisanship.

It didn’t exactly work out that way in 2024.