On July 25 of last year, then Major Alexander Vindman listened, with other officials, to a conversation between Trump and the newly elected Ukrainian president, Volodymyr Zelensky. Vindman as the National Security Council’s director for European affairs had organized the call.

“I would like you to do us a favor,” Trump told Zelensky, working his way to the subject of Joe Biden: “There’s a lot of talk about Biden’s son, that Biden stopped the prosecution, and a lot of people want to find out about that, so whatever you can do with the attorney general would be great. Biden went around bragging that he stopped the prosecution, so if you can look into it …”

“Having seen something ‘questionable (in the call),’ Vindman properly notified his superiors,” former White House Chief of Staff John Kelly said. “When subpoenaed by Congress in the House impeachment hearings, Vindman complied and told the truth. He did exactly what we teach them to do from the cradle to the grave,” he said. “He went and told his boss what he just heard.”

Vindman made an official complaint to John Eisenberg, the chief NSC lawyer, and Michael Ellis, a White House lawyer and Eisenberg’s deputy. Vindman’s reporting set in motion all that was to come. A whistleblower shared details of the call, and Vindman later realized that he could be compelled to testify.