Former National Security Adviser John Bolton announced Monday that he will testify in the Senate impeachment trial if he’s subpoenaed.

He previously stated that he’d await a judge’s ruling, piggybacking on the case of his former deputy Charles Kupperman.

However, that case fell apart when the House withdrew its subpoena of Kupperman, opting to focus the proceedings on witnesses who were willing to come forward and using the rest as fodder for the White House obstruction argument. The House never issued a subpoena to compel Bolton’s testimony.

Back in November, Bolton skipped a scheduled hearing, but his lawyer indicated that he was not unwilling to talk, saying that he had firsthand knowledge of “many relevant meetings and conversations.”

Bolton also posted some tantalizingly cryptic tweets later that month, claiming that he had been banned from his account after his resignation.

Multiple witnesses place Bolton near the epicenter of the Ukraine pressure campaign as a fervent objector.

Former National Security Council Senior Director Fiona Hill testified that he told her to report the backchannel actions of Ambassador to the EU Gordon Sondland, acting White House Chief of Staff Mick Mulvaney and Trump lawyer Rudy Giuliani to the National Security Counsel’s top lawyer.

“I am not part of whatever drug deal Sondland and Mulvaney are cooking up,” Bolton allegedly said.

Hill also recounted that Bolton called Giuliani “a hand grenade who’s going to blow everybody up.”

Former top Ukraine diplomat Bill Taylor said that Bolton urged him to send a cable to Secretary of State Mike Pompeo to voice his concern about the withholding of Ukraine military aide.

Democrats have long been pushing for Bolton to testify, and Sen. Minority Leader Chuck Schumer (D-NY) named him as one of four desired witnesses in a letter to Sen. Majority Leader Mitch McConnell (R-KY) just two weeks ago. McConnell rejected the request.

However, four Republican defections would take the decision out of McConnell’s hands, leaving it up to Supreme Court Chief Justice John Roberts to cast a tie-breaker vote whether or not to compel the witness to appear.

Read Bolton’s full statement here: