The Guardian’s Julian Borger has background on Marie Yovanovitch:

Since leaving Kyiv, Yovanovitch has been on sabbatical at the Institute for the Study of Diplomacy at Georgetown University, but is still a serving foreign service officer.

Her reported decision to appear seems to be in defiance of a block imposed by the secretary of state, Mike Pompeo, ordering state department officials not to give depositions to the congressional impeachment hearings. It is unclear whether the Trump administration will take further measures to try to stop her, in which case the Democrats running the House committees leading the impeachment investigation have signaled they are ready to issue friendly subpoenas.

First Pompeo yanks her out of Ukraine at Trump’s behest, then he orders state department officials to refuse to answer Congress’s questions. They think they have already completed the coup.

Pompeo’s claim that the House committees were seeking to “intimidate, bully and treat improperly” state department officials has drawn accusations of hypocrisy, particularly in light of his treatment of Yovanovitch.

He appears to have bowed to pressure from the White House by pulling her out of Kyiv two months before her posting was due to end, and failed to speak out in her defence when she was smeared by rightwing pundits and talkshow hosts.

Pompeo likes to claim he has brought “swagger” to the state department, but the treatment of Yovanovitch and the state department’s embroilment in the impeachment scandal has badly hit morale at the organisation.

Fuck swagger. Swagger is a Trump thing, an aggressive guy thing, a bully thing; at the extreme an authoritarian and/or fascist thing. Pompeo is a Tea Party hack and a very bad man.

In picking on Yovanovitch, the detractors have chosen a tough target. She has had a stellar career, serving as ambassador under three presidents to three countries (a rare distinction), Kyrgyzstan, Armenia and Ukraine, as well as senior adviser to the under secretary of state for political affairs.

She is one of the state department’s foremost experts on Russia, Ukraine and the surrounding region. She was born in Canada to Soviet emigrants and grew up speaking Russian, and is known to friends and colleagues as Masha. Her parents moved to the US when she was young and she became a naturalised US citizen in her teens, studying history and Russian studies at Princeton, and doing her postgraduate studies at the Pushkin Institute and the National War College.

Former colleagues all describe her as meticulous, calm under pressure, supremely qualified and steeped in the nonpartisan culture of professional diplomacy, all which set her apart from the campaign donors who are given an increasing share of ambassadorial posts.

In other words all of which set her apart from the people who buy an increasing share of ambassadorial posts.

After Trump’s election, according to former officials, Yovanovitch lost a good deal of her clout because the Ukrainians to whom she was talking began to suspect she was not speaking for the White House, which had its own agenda. Lutsenko and others looked instead for other channels, like Trump’s personal lawyer, Rudy Giuliani.

That split widened when Yovanovitch would not help Giuliani look for compromising material about Hunter Biden, the son of the Democratic frontrunner for next year’s presidential election.

“She refused to allow her embassy to be dragged into some sort of effort to concoct dirt for political purposes,” a former official said, adding that she was also not prepared to bend the rules by using personal devices for off-the-books conversations, a mistake made by the former special envoy to Ukraine, Kurt Volker. Volker’s messages, reflecting enthusiastic cooperation with Giuliani, made him look complicit. He has resigned from that part-time envoy job and also lost his academic post.

What Trump said about Yovanovitch on that phone call:

Months after the US Ambassador to Ukraine was unexpectedly recalled from her post, President Donald Trump disparaged the career diplomat in a call with his Ukrainian counterpart, a White House transcript released on Wednesday revealed.

Trump’s comments about Marie Yovanovitch — a member of his own country’s diplomatic corps — are a stunning breach of norms, former officials say, and lend credence to the claim that her early departure from the post was politically motivated.

“The former ambassador from the United States, the woman, was bad news and the people she was dealing with in the Ukraine were bad news so I just want to let you know that,” Donald Trump told Volodymyr Zelensky in a July 25 call, according to a White House transcript released Wednesday.

Zelensky, who was elected in April 2019, echoed the US President’s sentiment, saying “I agree with you 100%.”

“She’s going to go through some things,” Trump added.

Tables turned, except this time it’s not a criminal in a secretive phone conversation the transcript of which will be hidden in a Top Secret file where it doesn’t belong. This time it’s “the woman” talking to Congress in a closed but far from secret session of the impeachment inquiry. Donnie the rat is going to go through some things.