Donald Trump

Democrats announced an official impeachment inquiry into Trump on 24 September following a whistleblower’s complaint about Trump’s interactions with the president of Ukraine. A White House summary of a 25 July call shows Trump pressed Volodymyr Zelenskiy to work with the US attorney general and Rudy Giuliani, to investigate his political rival Joe Biden in the run-up the 2020 US election. Trump told Zelenskiy to look into unfounded and debunked allegations that Biden helped remove a Ukrainian prosecutor who investigated a company tied to his son Hunter.

Volodymyr Zelenskiy

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Ukraine’s new president was a wildcard candidate who had no experience of politics save for playing the president in a TV comedy. In a remarkable plot twist, he’s now been thrust into the centre of an American political scandal. “I don’t want to be involved in democratic elections of the USA,” Zelenskiy said in September, visibly embarrassed after the release of the summary. “We had a good phone call. It was normal. You read it. Nobody pushed me.”

Joe Biden

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Currently a strong candidate in the 2020 race for the Democratic presidential nomination, Biden was vice-president in 2016, when the Obama administration pressured Ukraine to remove Viktor Shokin, the country’s top prosecutor: the US and other western countries said Shokin was corrupt. There is no evidence of wrongdoing by Biden. “This is not a Republican issue or a Democratic issue. It is a national security issue,” Biden said.

Hunter Biden

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Joe Biden’s second son served on the board of Burisma Holdings, a Ukrainian gas producer, from 2014 to 2019. Burisma had been investigated by Shokin for alleged corruption, but the investigation had been dropped by the time the US government urged Ukraine to fire Shokin.

Viktor Shokin

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The former Ukrainian prosecutor general was widely seen as having blocked the prosecutions of corrupt oligarchs. Reform-minded Ukrainian politicians and international partners pressured the Ukrainian government to remove him for some time, and he was finally dismissed in 2016. He was later reinvented as a kind of heroic victim by Giuliani, who claimed – without evidence – that Shokin was fired on Biden’s orders.

Rudy Giuliani

The former mayor of New York is Trump’s personal attorney, most strident TV defender and, it seems, an occasional diplomat. The rough transcript of the Trump-Zelenskiy phone call shows Trump telling the Ukraine president to work with Giuliani in investigating Joe Biden. Trump also repeatedly told US officials running Ukraine policy to “talk to Rudy”, they said. But US officials testified they were alarmed by Giuliani’s role, which included a campaign against ambassador Marie Yovanovitch.

William ‘Bill’ Barr

The attorney general is named by Trump in the call with Zelenskiy, the president saying Zelenskiy should work with Barr to investigate a conspiracy theory blaming Ukraine, instead of Russia, for 2016 election tampering. The Department of Justice, which Barr oversees, said Trump had not asked Barr to work with Ukraine. The DoJ examined the Trump-Zelenskiy call but decided not to open an investigation – a decision which has been criticized by legal analysts.

The whistleblower

The anonymous author of a detailed complaint in mid-August that set the impeachment inquiry in motion, warning that Trump was “using the power of his office to solicit interference from a foreign country in the 2020 US election”. The account has been corroborated by witness testimony and public statements by Republicans. Yet Trump, in an apparent attempt to deflect attention from his alleged misconduct, has led a campaign to unveil the whistleblower, whose identity is purportedly protected by federal law.

Kurt Volker

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The former US special envoy to Ukraine resigned from the state department and met with congressional investigators, turning over records of WhatsApp chats in which he and other US diplomats worked to arrange a deal between Zelenskiy and Trump in which Trump would invite Zelenskiy to the White House and Zelenskiy would make a public statement that Ukraine had opened investigations of Burisma and election tampering. “I think Potus really wants the deliverable,” Gordon Sondland, the US ambassador to the European Union, said on the chats.

Gordon Sondland

A wealthy hotelier, Trump mega-donor and now US ambassador to the European Union. In the chats turned over by Volker, Sondland, whose usual portfolio does not include Ukraine, pushed Volker and a third diplomat, Bill Taylor, to get what Trump wanted from Zelenskiy. In closed-door testimony, Sondland initially said he took Trump at his word that there “was no quid pro quo”. Sondland later revised his testimony, saying, “I now recall speaking individually with [Zelenskiy aide Andriy] Yermak, where I said that resumption of US aid would likely not occur until Ukraine provided the public anti-corruption statement that we had been discussing for many weeks.”

William ‘Bill’ Taylor

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A public servant for 50 years, the former military officer was appointed ambassador to Ukraine by George W Bush and asked by Trump to take charge of the embassy in Kyiv. Taylor delivered testimony in October seen as devastating. He described how diplomats and Giuliani pursued Trump’s demand that Zelenskiy go on CNN and announce of investigation of Biden. Taylor said Sondland told him that both military aid and a White House visit – “everything” – hinged on Zelenskiy’s willingness to announce the investigation.In the chats, Taylor repeatedly expressed alarm about the deal Sondland was trying to put together. “As I said on the phone, I think it’s crazy to withhold security assistance for help with a political campaign,” Taylor wrote.

Taylor was scheduled to be the first witness to testify in public hearings.

George P Kent

A deputy assistant secretary of state, Kent was nominally in charge of Ukraine policy – until Trump reportedly put Giuliani and his EU ambassador in charge instead. Kent testified that Trump wanted to hear three words out of the Ukrainian president’s mouth: “investigations”, “Biden” and “Clinton”. Kent described his outrage over the plot to destroy the career of ambassador Marie Yovanovitch, which he attributed to “two snake pits” in Ukraine and the US. “I was told to keep my head down,” he said, “and lower my profile in Ukraine.”

Kent was scheduled to be the second witness to testify in public hearings.

Marie Yovanovitch

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Yovanovitch was US ambassador to Ukraine for almost three years before being unexpectedly recalled by Trump in May this year. US officials have described a plot – successful, it turned out – by her political enemies in Ukraine to destroy her ambassadorship. Trump criticized Yovanovitch in his call with Zelenskiy, saying, “Well, she’s going to go through some things.” “I didn’t know what it meant,” said Yovanovitch. “I was very concerned. I still am.” In March, Yovanovitch called on Ukraine to do more to address corruption. Then Ukraine prosecutor general Yuri Lutsenko accused Yovanovitch of giving Ukraine “a list of people whom we should not prosecute”. Lutsenko has since said Yovanovitch did not give him such a list.

Yovanovitch was scheduled to be the third witness to testify in public hearings.

Joseph Maguire

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The acting director of national intelligence only took on the role on 16 August. Maguire has been criticized for not sharing the whistleblower’s complaint with Congress – as is normal procedure. The acting director said he thought issues raised in the complaint might be covered by executive privilege, and said he consulted with officials at the justice department and White House lawyers over whether to pass the complaint to Congress. The White House eventually published the complaint.

Michael Atkinson

After receiving the complaint, Atkinson, the inspector general for the intelligence community, recommended it be shared with Congress. This put Atkinson at odds with his superior, Maguire, who blocked it from being shared. While the complaint was being withheld, Atkinson alerted lawmakers to its existence, saying it raised issues of “urgent concern”.

Nancy Pelosi

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The speaker of the House, and the most powerful woman in Congress, Pelosi decided to initiate an impeachment inquiry after the rough transcript of the Trump-Zelenskiy call was published. In doing so, Pelosi succumbed to long-mounting pressure from Democratic members of Congress, some of whom had been pushing for an impeachment inquiry to begin for more than a year.

Yuriy Lutsenko

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A veteran on the political scene, Lutsenko replaced Shokin as Ukraine’s prosecutor general but was also viewed with suspicion by reformers. Lutsenko met Giuliani and appears to have been amenable to opening an investigation into unsubstantiated claims of Ukrainian interference in the 2016 US election on behalf of the Democrats. Ukrainian officials have denied any effort to help Hillary Clinton in the election.

Serhiy Leshchenko

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One of the new brand of politicians who entered the scene after Ukraine’s Maidan revolution, Leshchenko was a leading political journalist who wrote widely on corruption and became an MP. In May 2016, he published information from a so-called “black ledger” that showed under-the-table payments from the pro-Russian former Ukrainian president Viktor Yanukovych’s regime to figures including Trump’s then campaign manager Paul Manafort. This led to Manafort’s resignation. Leshchenko later became an adviser to Zelenskiy and has said that before this week, it was “a clear fact that Trump wants to meet [Ukrainian officials] only if Biden case will be included”.