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Former President Donald Trump published a letter Friday ripping the House Select Committee on Jan. 6 for failing to investigate what he considers basic questions surrounding the riot.

The committee issued a subpoena for testimony from Trump at its business meeting Thursday.

The letter, dated Thursday, opened with Trump's unproven claims that the 2020 election was "stolen" before directly addressing the Jan. 6 committee and questioning its purpose.

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At no point in his memo did Trump clarify if he would be honoring the subpoena or ignoring it.

Picture of the Jan. 6 House Select Committee

Rep. Bennie Thompson, D-Miss., makes remarks during a hearing of the Select Committee to Investigate the January 6th Attack on the United States Capitol. (Tom Williams/CQ-Roll Call, Inc via Getty Images)

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"The Unselect Committee has willfully ignored the fact that days before January 6, 2021, I recommended and authorized thousands of troops to be deployed to ensure that there was peace, safety, and security at the Capitol and throughout Washington, D.C. on January 6th because I knew, just based on instinct and what I was hearing, that the crowd coming to listen to my speech, and various others, would be a very big one, far bigger than anyone thought possible," Trump wrote.

Read the Trump letter:

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Trump's arguments against the continued efforts of the Jan. 6 committee hit similar points as wider criticism against the investigation by conservative groups.

House Republicans have finalized a report outlining the intelligence and security failures that occurred during the Jan. 6, 2021, assault on the U.S. Capitol. 

An image of former President Donald Trump is displayed during a hearing by the House Select Committee to Investigate the January 6th Attack on the U.S. Capitol in the Cannon House Office Building in Washington, D.C., on Thursday. (Drew Angerer/Getty Images)

"The Department of Defense timeline shows that National Guard troops could have easily been present at the Capitol before January 6th and that I fully authorized this recommendation and request. Following my authorization, the Department of Defense was surprised to receive a wholesale refusal, in writing, from D.C. Mayor Muriel Bowser and the Capitol Police, who do not report to me, but report to Speaker of the House Nancy Pelosi. The law requires their authorization before any troop deployment could be utilized in Washington, D.C."

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Jan 6 violent insurrection

In this Jan. 6, 2021, file photo, violent rioters, loyal to President Donald Trump, storm the Capitol in Washington, D.C. (AP Photo/John Minchillo, File)

"Why the failure to act or use this ready force?" Trump asked in his letter.

The former president went on to use the opportunity to take shots at the continued investigations of the committee and mock the lack of coverage given to the hearings.

"Despite very poor television ratings, the Unselect Committee has perpetuated a Show Trial the likes of which this Country has never seen before. There is no Due Process, no Cross-Examination, no 'real' Republican members, and no legitimacy since you do not talk about Election Fraud or not calling up the troops. It is a Witch Hunt of the highest level, a continuation of what has been going on for year," Trump teased.

Trump speaking in North Carolina

Former President Donald Trump speaks at a Save America Rally in Wilmington, North Carolina, on Sept. 23, 2022. (Allison Joyce/Getty Images)

Rep. Liz Cheney, R-Wyo., offered the subpoena motion after members made a presentation on Trump's role in the Jan. 6 attack on the Capitol by Trump supporters. The committee's vote was unanimous.

"We must seek the testimony under oath of January 6th's key player," Cheney said of the motion to compel testimony from Trump.

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Trump has not only rejected overtures to testify before the panel, but he has called on allies and former staff to do likewise.

Fox News' Haris Alec and Tyler Olson contributed to this report.