Rudy Giuliani was mentioned more than 430 times during House impeachment investigators' interviews with two key U.S. diplomats, transcripts released on Tuesday show, underscoring the former New York mayor's outsized role in U.S.-Ukraine policy.

More than anyone else, Giuliani shaped Trump's view of Ukraine and caused headaches for top State Department officials, as Gordon Sondland, the U.S. ambassador to the European Union and Kurt Volker, then the U.S. special representative for Ukraine, detailed in their testimonies last month.

Here are some of the most noteworthy references to Giuliani in those documents:

Sondland said officials were "disappointed" by Trump's "direction that we involve Mr. Giuliani" in Ukraine policymaking. "Based on the President's direction we were faced with a choice. We could abandon the goal of a White House meeting for President [Volodymyr] Zelenskiy ... or we could do as President Trump directed and talk to Mr. Giuliani to address the president's concerns."

Sondland said Trump did not make clear during a meeting earlier this year what Giuliani's concerns with regard to Ukraine were. "He wasn't even specific about what he wanted us to talk to Giuliani about. He just kept saying: Talk to Rudy. Talk to Rudy."

Sondland said Giuliani "specifically mentioned the 2016 election, including the DNC server, and Burisma as two anti-corruption investigatory topics of importance for the president."

Giuliani and Trump were pushing for Zelenskiy to make what was deemed an "anti-corruption" statement, and Sondland testified that he and Volker had to workshop that statement so Giuliani would be satisfied. "I was concerned about was that Zelenskiy would say whatever he would say on live television and it still wouldn't be good enough for Rudy, sIash, the president, and then we would be having to go back and tell Zelensky, 'sorry, not good enough,' and that would be extremely embarrassing."

Regarding the statement, "Giuliani was the one that had to be satisfied," Sondland said.

Sondland said there were multiple conference calls to discuss the wording of the statement that would satisfy Giuliani. "I believe it then morphed when we started to work on the statement, it morphed from the vanilla corruption into the Burisma/[2016] portion."

“All I can recall is the gist of every call was what was going to go in the press statement,” Sondland testified. Giuliani "kept repeating Burisma and 2016 election. He never mentioned Biden to me on any call that I was on."

"I think Volker was trying to get to the bottom of what was it that the President wanted to see from the Ukrainians in order to get the White House visit scheduled. And I think Giuliani kept saying it needs to be some kind of a public utterance," Sondland added.

Sondland said Pompeo expressed annoyance with Giuliani's involvement in foreign affairs. "And Pompeo rolled his eyes and said: 'Yes, it's something we have to deal with.'" He added the State Department was "fully aware" of the issue but "there was very little they could do about it if the president decided he wanted his lawyer involved."

Giuliani drove Trump's negative view of Ukraine, Volker testified, describing the president's comments from an Oval Office meeting this year. "During the course of this conversation, he did reference Mayor Giuliani, because he said that what we were saying as a positive narrative about Ukraine is not what he hears. And he gave the example of hearing from Rudy Giuliani that they're all corrupt, they're all terrible people, that they were — they tried to take me down — meaning the president in the 2016 election. And so he was clearly demonstrating that he had a negative view of and that information that he was getting from other sources was reinforcing that negative view."

On the statement they attempted to have the Ukrainians read, Volker recalled Giuliani saying: "'Well, if it doesn't say Burisma and if it doesn't say 2016, what does it mean? You know, it's not credible. You know, they're hiding something.' And so we talked and I said: 'So what you're saying is just at the end of the same statement, just insert Burisma and 2016, you think that would be more credible? And he said: 'Yes.'"