House impeachment investigators released hundreds of pages of previously secret testimony Monday, revealing troubling allegations about President Donald Trump's involvement in the removal of a respected American ambassador and the use of U.S. foreign policy to advance his political interests.

The transcripts, featuring former U.S. Ambassador to Ukraine Marie Yovanovitch and former senior State Department adviser Michael McKinley, provide new details about the growing impeachment investigation and the treatment of career diplomats under the Trump administration.

Ambassador Describes Campaign to Remove Her

Yovanovitch, a veteran diplomat who was abruptly recalled from Ukraine in May, testified that she became the target of a campaign involving Trump's personal attorney, Rudy Giuliani, and Ukrainian figures seeking her removal.

According to her testimony, unfounded accusations about her loyalty to Trump circulated among the president's allies, despite her longstanding reputation for fighting corruption in Ukraine.

Yovanovitch described receiving an urgent call directing her to leave Ukraine immediately. When she questioned the decision, she was given little explanation beyond concerns about her security.

She also testified that Deputy Secretary of State John Sullivan acknowledged she had done nothing wrong.

The ambassador expressed particular concern about Trump's July 25 telephone conversation with Ukrainian President Volodymyr Zelensky, during which Trump described her as bad news and suggested she would face consequences.

Asked whether she felt threatened by the president's remarks, Yovanovitch answered, "Yes."

State Department Official Resigns in Protest

McKinley, a career diplomat with 37 years of Foreign Service experience, testified that he resigned in October partly because of the State Department's failure to defend Yovanovitch.

He described repeatedly raising concerns with Secretary of State Mike Pompeo and attempting to secure a public statement supporting the ambassador.

According to McKinley, Pompeo ultimately declined to issue the statement.

McKinley also expressed alarm about what he viewed as efforts to use American diplomatic personnel to obtain politically damaging information about Trump's domestic opponents.

His testimony raises additional questions about whether the administration's foreign policy machinery was being used to benefit the president's reelection prospects.

Impeachment Investigation Enters Public Phase

The release marks a significant development in the House investigation into Trump's dealings with Ukraine.

Investigators are examining whether the president improperly pressured Zelensky to announce investigations involving former Vice President Joe Biden, a potential opponent in the 2020 presidential election.

The inquiry also involves the administration's decision to withhold nearly $400 million in congressionally approved military assistance to Ukraine.

Trump has repeatedly denied wrongdoing, describing his conversation with Zelensky as appropriate and condemning the impeachment investigation as politically motivated.

Republicans have criticized Democrats for conducting closed-door depositions and demanded greater transparency. The release of these transcripts begins addressing those demands as lawmakers prepare for public hearings.

House Intelligence Committee Chairman Adam Schiff said the documents would allow Americans to examine the evidence collected by investigators.

The testimony presents a disturbing account of career diplomats caught between established American foreign policy and political demands from the president's allies.

With additional transcripts expected in the coming days, the impeachment investigation is entering a more public and potentially consequential stage.