The House Intelligence Committee said Monday that it had subpoenaed Rudy Giuliani for documents related to his work in Ukraine—a major step in the investigation into efforts by President Donald Trump and his personal attorney that involved digging up dirt in Ukraine on 2020 Democratic presidential candidate Joe Biden.

The subpoena is part of an investigation by the House Foreign Affairs, Intelligence, and Oversight committees into Trump and Giuliani’s communications with Ukrainian President Volodomyr Zelensky and his advisors. The congressional committees also sent letters to three Giuliani associates involved in his Ukraine work asking them to hand over documents and appear for depositions next month.

For roughly a year, Giuliani sought to elicit information from Ukrainians on possible origins of the Mueller investigation, as well as on Biden’s son, Hunter, and his role on the board of directors of a major gas company. Giuliani said that in recent months the State Department helped him get in touch with Zelensky administration officials.

Giuliani and Trump were both subjects of a whistleblower complaint filed August 12 which outlined some of the ways they asked Ukrainians to investigate the Bidens.

Since the complaint became public last week, Giuliani has appeared on multiple television shows to defend his work regarding Ukraine and underline his communication with State Department officials about his efforts.

“In addition to this stark admission, you stated more recently that you are in possession of evidence—in the form of text messages, phone records, and other communications—indicating that you were not acting alone and that other Trump Administration officials may have been involved in this scheme,” Rep. Eliot Engel, chairman of the House Foreign Affairs committee, wrote in a letter to Giuliani. Engel requested Giuliani produce the records no later than October 15.

The Trump lawyer did not immediately respond to a request for comment on this story.

But Giuliani previously told The Daily Beast he would not be willing to appear for questioning on Capitol Hill, and has repeatedly accused Democratic lawmakers and committee chairs of being “corrupt” and operating in bad faith. And Democrats worry that Giuliani appearing publicly could hinder the impeachment inquiry by turning the hearing into a spectacle.

Even before this probe was launched, whenever the topic of document subpoenas from the Democratic House majority came up, the Trump attorney and former New York City mayor typically reacted in a hostile manner. “If they want to come after me, I gladly accept it, because we could just make the Biden stuff bigger news,” Giuliani told The Daily Beast in early June—when congressional Democrats had begun discussing opening a probe into Giuliani’s overseas work. “Do it!… I think it’d be a fun fight.”

Throughout this whole saga, Giuliani has done his Ukraine and Biden work with the explicit blessing from his client, President Trump. In fact, the president was so into it that he even made a specific point of privately instructing Giuliani to keep doing more TV interviews and cable news hits on the topic, so that Trumpworld could train as much media attention as possible on the Bidens.

In the time since all of this broke, the president, the Republican National Committee, the Trump reelection campaign, numerous GOP allies on Capitol Hill, and various other major organs of the party have rallied in Giuliani’s defense and to his cause. Democrats, meanwhile, have started the single biggest impeachment push of the Trump era thus far.

Giuliani is just the latest Trump adviser to hear from the committees. Last week, the three congressional panels subpoenaed Secretary of State Mike Pompeo for related documents and announced depositions for five current and former State Department employees, including Kurt Volker, the former U.S. representative for Ukraine negotiations who resigned from his post Friday.