During nearly 10 hours of testimony to House impeachment investigators behind closed doors Monday, President Donald Trump's former top Russia adviser Fiona Hill alleged that acting chief of staff Mick Mulvaney, former ambassador to the European Union Gordon Sondland, and the president's personal lawyer Rudy Giuliani were running a "rogue operation" in Ukraine that sought to bypass official channels to benefit Trump politically.

Hill's testimony for the first time directed serious attention to the key role Mulvaney played in Trump's months-long attempt to pressure Ukraine to investigate former Vice President Joe Biden, an effort that led House Democrats to launch an impeachment inquiry last month.

"Rudy Giuliani has clearly been a leading force for the administration in defining a shadow foreign policy in Ukraine."

—Rep. Jamie Raskin

During her deposition, according to the Wall Street Journal, Hill "detailed a July 10 meeting she attended with senior Ukrainian officials, then-national security adviser John Bolton, and other U.S. officials in which the U.S. ambassador to the European Union, Gordon Sondland, raised the issue of the investigations" into Biden.

"Both Ms. Hill and Mr. Bolton left the meeting with concerns about what had transpired, and Ms. Hill said Mr. Bolton instructed her to talk to [National Security Council] lawyer John Eisenberg," the Journal reported. "Mr. Sondland also appeared to be coordinating his efforts with acting White House chief of staff Mick Mulvaney."

Mulvaney's role in Trump's push for a Biden probe in Ukraine was first revealed last month, when reports emerged that the U.S. president ordered Mulvaney—who also runs the Office of Management and Budget—to put a hold on around $400 million in military aid to Ukraine.

According to text messages released by House Democrats earlier this month, top Ukraine diplomat Bill Taylor raised alarm about Trump's decision to withhold assistance in an apparent bid to extract political favors from the Ukrainian government.

For the first real time, some heat being put on Mulvaney (who largely escaped a lot of scrutiny even after it was reported that the he was involved in holding up the funding) https://t.co/drE1aQ9Anq — Sam Stein (@samstein) October 15, 2019

As the New York Times reported Monday night, Bolton, who departed the White House last month, likened Sondland and Mulvaney's secretive activities to a "drug deal" and attempted to distance himself from the officials' scheming.

"I am not part of whatever drug deal Sondland and Mulvaney are cooking up," Bolton instructed Hill to tell White House lawyers, according to the Times, which cited two people who attended Hill's deposition.

While critics were quick to caution against hailing Bolton—an architect of the catastrophic and illegal invasion of Iraq—as any kind of hero, they said his private objections lay bare the flagrant illegality of the White House's shadow operation in Ukraine.

Just a reminder, John Bolton is closer to being a war criminal than a hero. Whatever he did or said in private, he hasn’t done or said anything publicly. Nor did he, when he was in a position to do so, actually do anything to stop the crime he saw. He just tried to cover his ass. — Stephen Miles (@SPMiles42) October 15, 2019 John Bolton is a scummy scumbag who was a key architect of the plot to lie to the country about Saddam having WMD. But Trump, Guiliani, and Mulvaney's drug deal was so illegal and so immoral that it offended even Bolton's sense of right and wrong. This is where we are now. — Robert Murphy (@robertemilem) October 15, 2019

Following Hill's testimony, Rep. Jamie Raskin (D-Md.) told reporters that her deposition confirmed "Rudy Giuliani has clearly been a leading force for the administration in defining a shadow foreign policy in Ukraine."

As the Times reported,

Ms. Hill, the senior director for European and Russian affairs, testified that Mr. Giuliani and his allies circumvented the usual national security process to run their own foreign policy efforts, leaving the president's official advisers aware of the rogue operation yet powerless to stop it. At one point, she confronted Mr. Sondland, who had inserted himself into dealings with Ukraine even though it was not part of his official portfolio, according to the people informed about Ms. Hill's testimony. He told her that he was in charge of Ukraine, a moment she compared to Secretary of State Alexander M. Haig Jr.'s declaration that he was in charge after the Ronald Reagan assassination attempt, according to those who heard the testimony. According to whom, she asked. The president, he answered.

Thanking Hill for her detailed testimony, Rep. Ted Lieu (D-Calif.) tweeted Monday night, "The truth will keep coming out. And Trump cannot stop it."