In the whistleblower complaint that triggered the impeachment inquiry, the author describes a series of events – partly public and partly described by other officials – that culminated in a call between President Donald Trump and Ukrainian President Volodymyr Zelensky.

We've arranged those alleged events in chronological order – providing a clearer context to the call in which Trump pressed Zelensky to investigate 2016 election interference and the Biden family's Ukrainian business dealings.

December 2018: Trump's personal lawyer Rudy Giuliani speaks with Viktor Shokin, Ukraine's former prosecutor general.

January: Giuliani meets with Yuriy Lutsenko, Ukraine's prosecutor general under President Petro Poroshenko, in New York.

February: Giuliani meets with Lutsenko a second time in Warsaw, Poland.

March: 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.

U.S. Ambassador Marie Yovanovitch obstructing Ukrainian investigation of such involvement.

Former Vice President Joe Biden trying to protect his son's business with Ukraine.

April 21: Zelensky defeats Poroshenko in Ukrainian presidential elections. Trump makes a brief congratulatory call to Zelensky.

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."

April 29: U.S. Ambassador Yovanovitch is recalled to Washington for "consultations."

May 6: The State Department announces Yovanovitch will end her assignment in Kyiv, Ukraine's capital.

May 9: The New York Times reports that Giuliani plans to travel to Ukraine to press the government to pursue investigations into election interference in 2016 and alleged wrongdoing by the Biden family.

May 10: Trump saysin an interview with Politico that he "plans to speak with Giuliani about the trip." Hours later, Giuliani cancels his trip because Zelensky was "surrounded by enemies of the [U.S.] president ... and of the United States."

May 11: Lutsenko meets with President-elect Zelensky and expresses his wish to remain prosecutor general in the new government.

May 14: Giuliani says in an interview with a Ukrainian journalist that the U.S. ambassador was "removed ... because she was part of the efforts against the president."

Around May 14: Trump instructs Vice President Mike Pence to cancel his trip to Ukraine to attend Zelensky's inauguration.

June 13: Trump tells ABC's George Stephanopoulos that he "would accept damaging information on his political rivals from a foreign government."

June 21: Giuliani tweets, "New Pres. of Ukraine still silent on investigation of Ukrainian interference in 2016 election and alleged Biden bribery of Pres Poroshenko. Time for leadership and investigate both if you want to purge how Ukraine was abused by Hillary and Obama people."

New Pres of Ukraine still silent on investigation of Ukrainian interference in 2016 election and alleged Biden bribery of Pres Poroshenko. Time for leadership and investigate both if you want to purge how Ukraine was abused by Hillary and Obama people. — Rudy Giuliani (@RudyGiuliani) June 21, 2019

July 18: An Office of Management and Budget official says Trump issued instructions to suspend U.S. aid to Ukraine.

July 25: Trump phones Zelensky to request that Ukraine investigate 2016 election interference and alleged corruption by the Biden family. Trump asks Zelensky to meet with Giuliani and Attorney General Barr for further discussions.

July 25 evening: A post on the Ukrainian president's website mentions the call: "Trump expressed his conviction that the new Ukrainian Government will be able to ... complete the investigation of corruption cases that have held back cooperation between Ukraine and the U.S."

July 26: Senior White House officials intervene to "lock down" all records of the phone call and load the transcript into a separate electronic server, according to the whistleblower's complaint.

July 26: Kurt Volker, U.S. representative for Ukraine, and Gordon Sondland, U.S. ambassador to the European Union, meet with Zelensky to provide advice.

August 2: Giuliani travels to Madrid to meet with a Zelensky adviser as a "follow-up" to the call.

Aug. 9: Trump says he thinks Zelensky "will be invited to the White House."