Here is the timeline of recent key events and stories surrounding Trump, Ukraine and the intelligence whistleblower.
Washington: US President Donald Trump's impeachment process began after a whistleblower filed an official complaint that the President was discussing former Vice President Joe Biden with Ukraine's president and has misused his official power.
A transcript of the conversation released by the White House showed that Trump repeatedly pushed Zelensky to investigate former Vice President Joe Biden and his son, Hunter. There is no evidence of wrongdoing by either Joe or Hunter Biden.
Even before the whistleblower complaint was made available to lawmakers, House Speaker Nancy Pelosi on Tuesday declared Trump had betrayed his oath of office and announced she was opening a formal impeachment inquiry into the President.
Here is the timeline of recent key events and stories surrounding Trump, Ukraine and the intelligence whistleblower:
May 13, 2014: Hunter Biden, the son of then-Vice President Joe Biden, joins the board of the Ukrainian energy company --- Burisma Holdings. It is owned by oligarch Mykola Zlochevsky, one of the several of the Ukrainian corruption probe.
December 2015: Joe Biden travels to Ukraine, giving a speech that touches on concerns about corruption in the country. At some point, he tells Ukrainian leaders to fire Ukrainian prosecutor general Viktor Shokin or lose more than USD 1 billion in loan guarantees. Biden joins many Western leaders in urging Shokin’s ouster.
March 29, 2016: Shokin is ousted from his position by Ukraine’s parliament.
May 12, 2016: Yuri Lutsenko becomes prosecutor general of Ukraine, replacing Shokin.
December 2018: Trump's personal lawyer Rudy Giuliani speaks with Viktor Shokin, Ukraine's former prosecutor-general.
January 2019: Giuliani meets with Yuriy Lutsenko, Ukraine's prosecutor general under President Petro Poroshenko, in New York.
February 2019: Giuliani meets with Lutsenko a second time in Warsaw, Poland.
March 2019: In a series of articles in The Hill, Lutsenko and other Ukrainian officials make claims about: Ukrainian involvement in the 2016 election, allegedly in collaboration with the Democratic National Committee, US Ambassador Marie Yovanovitch obstructing Ukrainian investigation of such involvement and Former Vice President Joe Biden trying to protect his son's business with Ukraine.
April 21, 2019: Volodymyr Zelensky wins Ukrainian election, beating incumbent Petro Poroshenko. Trump calls Zelensky to congratulate him and discusses “reforms that strengthen democracy, increase prosperity, and root out corruption” according to a White House readout of the call.
April 25: In a Fox News interview, Trump describes Lutsenko's claims as "big" and "incredible" and says the attorney general "would want to see this."
May 6, 2019: State Department announces ambassador to Ukraine Masha Yovanovitch - a career diplomat - would end her assignment in Kyiv.
May 9, 2019: The New York Times reports Trump's personal attorney, Rudy Giuliani acknowledges that he plans to travel to Ukraine to urge the new government to investigate the role Biden’s son Hunter had in a gas company owned by a Ukrainian businessman.
Giuliani says he will also press for a review of allegations circulating in conservative circles that Ukraine may have helped Hillary Clinton’s campaign. Giuliani cancels the trip amid criticism but continues his lobbying campaign over ensuing months.
May 10, 2019: Trump tells Politico he plans to speak with Giuliani about the trip. Giuliani later cancels the trip, claiming Zelensky was “surrounded by enemies” of Trump.
May 14, 2019: In a published interview with a Ukrainian journalist, Giuliani says Yovanovitch had been removed because she had been working against Trump.
June 21, 2019: Giuliani complains in a tweet that Zelensky “still silent on the investigation of Ukrainian interference in 2016 and alleged Biden bribery” of Poroshenko.
July 18, 2019: An Office of Management and Budget official says Trump issued instructions to suspend US aid to Ukraine.
July 25, 2019: Trump has a phone call with Zelensky and asks him to speak to Attorney General William Barr and Giuliani about reopening a Ukrainian investigation into a Ukrainian gas company connected to Hunter Biden.
The Ukrainian readout describes Trump as “convinced that the new Ukrainian government will be able to quickly improve the image of Ukraine, complete investigation of corruption cases, which inhibited the interaction between Ukraine and the USA.”
A less detailed White House readout said Trump called Zelensky “to congratulate him on his recent election.”
July 26, 2019: Senior White House officials intervene to "lockdown" all records of the phone call and load the transcript into a separate electronic server, according to the whistleblower's complaint.
August 2, 2019: On or around this date, Giuliani travels to Madrid to meet Zelensky's adviser Andriy Yernak, which the whistleblower said was “a ‘direct follow-up’” to the July 25 Trump-Zelensky phone call.
August 8, 2019: Giuliani tells Fox News that US Attorney John Durham was investigating Ukraine. Durham had been named by Attorney General William Barr as part of a probe into the origins of the investigation into Russian election meddling and connects to the Trump campaign.
August 12, 2019: The inspector general of the intelligence community receives a complaint from a whistleblower describing an “urgent concern.”
Over the ensuing two weeks, Inspector General Michael Atkinson investigates the complaint, determines that it meets the definition of an “urgent concern,” which could include a violation of the law or executive order, and finds the complaint “credible.”
The whistleblower delivers his complaint to the chairmen of the intelligence committees of the Senate and House of Representatives.
August 28, 2019: Politico reports that Trump has put a hold on USD 250 million in military aid to Ukraine.
September 9, 2019: Atkinson reveals the existence of the whistleblower’s complaint to lawmakers and the refusal of the acting director of national intelligence, Joseph Maguire, to transmit it to the intelligence committees as directed by the law. Atkinson notes that Maguire disagreed with his conclusions and appeared to be treating the complaint differently than in similar past cases.
Three House committees launch investigation of efforts by Trump, Giuliani and others to pressure the Ukrainian government to assist the President's reelection efforts. The committees request information about Trump's July phone call with Zelensky.
September 11-12, 2019: In advance of a Senate Appropriations Committee vote designed to force the release of the USD 250 million military aid package.
September 13, 2019: The House intelligence committee chairman, Adam Schiff demands in letters that the whistleblower complaint is turned over to him in keeping with the law and past practice. Maguire refuses, and Schiff issues a subpoena for the complaint on September 13. Maguire again refuses, claiming Schiff does not have a right to the document under a technical reading of the stature because the complaint concerns the “conduct by someone outside the intelligence community.”
Maguire also says he is too busy to immediately testify before Schiff’s committee. A hearing is slated for September 26.
September 18, 2019: The Washington Post publishes first public account about the whistleblower complaint.
September 19, 2019: The Washington Post and The New York Times report that the whistleblower’s complaint involves Trump’s call with the Ukrainian president. Giuliani makes an appearance on CNN and acknowledges he pressed Ukraine to investigate Biden.
September 20, 2019: Trump is asked if he brought up Biden in the call with Zelensky. He replies, “It doesn’t matter what I discussed.” He also uses the moment to urge the media “to look into” Biden’s background with Ukraine.
A person who was briefed on the call said Trump urged Zelensky to investigate Biden’s son, Hunter, who worked for a Ukrainian gas company.
September 22, 2019: Donald Trump acknowledges that he discussed Joe Biden in a July call with Zelensky.
House Speaker Nancy Pelosi writes to the acting DNI stating that if the administration refusals continue, it would constitute a "serious possible breach of constitutional duties by" Trump and would take Congress "into a whole new stage of the investigation."
September 23, 2019: Trump tells reporters at the UN that his conversations with Ukraine's leaders were without fault and said he wanted the world to see what he said.
September 24, 2019: Trump tweets the White House will release a transcript of his call with Zelensky. House Speaker Nancy Pelosi announces formal impeachment inquiry into Trump.
September 25, 2019: Justice Department releases summary of Trump-Zelensky call. Trump and Zelensky meet in person for the first time at a UN gathering in New York.
September 26, 2019: House Intelligence Committee releases an unclassified version of a whistleblower complaint.