The top U.S. diplomat in Ukraine, William B. Taylor, didn’t hear firsthand some of the more damaging moments at issue in President Trump’s impeachment inquiry, but he was talking to people who were in all the rooms. So it makes sense that someone with his vantage point on this will be one of the Democrats’ first public witnesses as they open these hearings, starting with Taylor on Nov 13.

A little background is necessary. Taylor was installed in Ukraine in June by Secretary of State Mike Pompeo after Trump had ousted former Ukraine ambassador Marie Yovanovitch. Taylor is a career diplomat and Vietnam War veteran who has served under Republican and Democratic administrations. Key figures in all this, including ones who were Trump’s preferred point people, were open with Taylor as they tried to get Ukraine to do what Trump wanted.

What Taylor found, according to the transcript of his private deposition released on Wednesday, was this: Trump directed officials to tell Ukrainian officials that if they wanted their military aid and an Oval Office meeting, their president needed to publicly agree to investigate Democrats.

Taylor didn’t attribute this to one conversation with one person. Over the course of several months, he talked to high-level officials at the National Security Council, in Ukraine’s presidential office and two of the “three amigos” picked by Trump to head the central allegations in this impeachment inquiry. “I was in the regular channel” of diplomacy, Taylor testified, “but I was also in the irregular one.”

Taylor pieced it together after keeping what one House impeachment investigator said was “incredibly detailed” documentation that included a memo he wrote about some of this, a cable to Pompeo relaying his concerns, regular texts with two of the “three amigos” charged by Trump to work on Ukraine, texts he exchanged with Ukrainian officials, and his own handwritten notes. Taylor was like a reporter at the center of the action who had access to all the key players.

Here’s what he learned, and from whom, in those many conversations he had about the allegations at the center of the impeachment inquiry:

Then-national security adviser John Bolton: “He indicated that he was very sympathetic” to Taylor’s concerns that Trump was asking Ukrainian officials to do something they shouldn’t. This is important, because it suggests Trump’s top security official didn’t like what he heard, either. We’ve heard this in other testimony from Bolton’s deputies, but the House has yet to talk to Bolton. He would be a big get for them.

The chief of staff to Ukraine’s newly elected president: “I think it was becoming clear to the Ukrainians that, in order to get this meeting that they wanted, they would have to commit to pursuing these investigations,” Taylor said. He added they didn’t want to because they believed that opening an investigation into Burisma, the company Hunter Biden served as a board member, “would have involved Ukraine in the 2020 election campaign.” This is important because it suggests Ukrainian officials were aware there were conditions on the aid and meeting they wanted from Trump, conditions they also thought were too political to touch.

Gordon Sondland: The ambassador to the European Union, who was one of Trump’s unofficial point people on Ukraine, told Taylor he was under orders from Trump to tell Ukrainians they needed to start investigations. “He said that President Trump wanted President Zelensky in a box by making [a] public statement about ordering such investigations.” This is important, because it points to Trump as the person driving all of this.

NSC officials like Fiona Hill and Lt. Col Alexander Vindman, who heard Sondland tell Ukrainians they needed to start investigations: After talking to these officials, Taylor testified he gathered it was the “unanimous opinion of every level of interagency discussion” that the aid should be resumed “without delay."

Kurt Volker, the former special envoy to Ukraine: Taylor’s conversations with Volker corroborated much of what he heard from Sondland. “Here’s what I understood from Ambassador Volker and Ambassador Sondland: In order to get President Zelensky and President Trump in a meeting in the Oval Office, they took from that May 23rd meeting [with Trump] that they needed to work with Rudy Giuliani, so — and they did.”

An unnamed Office of Management and Budget official who says Trump ordered a hold on military aid: Here’s another instance where Taylor heard someone say the aid holdup came directly from Trump. “All that the OMB staff person said was that the directive had come from the president to the chief of staff to OMB,” Taylor said in his opening statement, about when he heard military aid was being held up, and being held at the direction of the president.

“In an instant, I realized that one of the key pillars for our strong support for Ukraine was contrary to the goals of longstanding U.S. policy,” he testified.

NSC Senior Director Tim Morrison: This was yet another conversation where Taylor heard that the conditions came directly from Trump. Taylor said Morrison told him: “President Trump did insist that President Zelensky go to a microphone and say he is opening investigations of Biden and 2016 election interference, and that President Zelensky should want to do this himself.”

State Department officials: They didn’t like Sondland working on the Ukrainian issue, according to Taylor: “There was some discomfort within the State Department with Ambassador Sondland’s role in Ukraine. Of course, Ukraine is not in the E.U..” It underscores how Trump had a less transparent unofficial diplomatic channel on Ukraine rather than the official one.