WASHINGTON (AP) — The House committee investigating the January 6 attack on the US Capitol formally issued an extraordinary subpoena to Donald Trump on Friday, demanding testimony from the former president who lawmakers say “personally orchestrated” a multi-part effort to overturn the results of the 2020 election.

The nine-member panel issued a letter to Trump’s lawyers saying he must testify, either at the Capitol or by videoconference, “beginning on or about” November 14 and continuing for multiple days if necessary.

The letter also outlined a sweeping request for documents, including personal communications between Trump and members of Congress as well as extremist groups. Those are to be turned in by November 4, although the committee’s deadlines are generally subject to negotiation.

“We recognise that a subpoena to a former president is a significant and historic action,” Chairman Bennie Thompson and Vice Chair Liz Cheney wrote in the letter to Trump. “We do not take this action lightly.”

The panel rooted its action in history, listing past presidents from John Quincy Adams to Gerald Ford, who testified before Congress after leaving office — and noted that even sitting presidents have responded to congressional subpoenas.

It is unclear how Trump and his legal team will respond. He could comply or negotiate with the committee, announce he will defy the subpoena or ignore it altogether. He could also go to court and try to stop it.

The subpoena is the latest and most striking escalation in the House committee’s 15-month investigation of the deadly January 6, 2021, insurrection, bringing members of the panel into direct conflict with the man they have investigated from afar through the testimony of aides, allies and associates.

In the letter, the committee wrote about the “overwhelming evidence” it has assembled, showing Trump “personally orchestrated” an effort to overturn his defeat in the 2020 election, including by spreading false allegations of widespread voter fraud, “attempting to corrupt” the Justice Department and pressuring state officials, members of Congress and his own vice president to change the results.

Lawmakers say key details about what Trump was doing and saying during the siege remain unknown. According to the committee, the only person who can fill the gaps is Trump himself.

The panel — comprised of seven Democrats and two Republicans — approved the subpoena for Trump in a surprise vote last week. Every member voted in support.