Former acting Defense Secretary Christopher Miller says in a forthcoming interview that former President TrumpDonald TrumpThe Memo: How the COVID year upended politicsBiden seeks his moment with pandemic address A year with the coronavirus: How we got hereMORE’s speech at a “Stop the Steal” rally on Jan. 6 was to blame for the deadly Capitol riot later that day.

Would anybody have marched on the Capitol, and overrun the Capitol, without the presidents speech? I think its pretty much definitive that wouldnt have happened, Miller said while speaking with Vice on Showtime.

Miller served as Trump’s final Defense chief, filling the top Pentagon post from November until Trump left office in January. Miller previously headed up the National Counterterrorism Center last year.

The former Defense chief told Vice that he wasnt sure whether or not Trump was aware of how consequential his speech would be, but said he believed there was a “cause-and-effect” relationship between the speech and riot.

The question is, did he know that he was enraging the crowd to do that? I dont know,” Miller said.

Vice noted that Miller faced criticism of his own due to the delayed deployment of the National Guard to the Capitol after a mob of Trump’s supporters had broken in on Jan. 6.

It comes back to understanding how the military worksthis isnt a video game, its not Black Ops Call of Duty, Miller said, rejecting the criticism.

A day before the Capitol attack, all 10 living former Defense secretaries released a letter advising Miller to ensure a peaceful transition of power, amid concerns that Trump would attempt to use the military to halt the transition process.

There was a lot of concern that we were just some sort of Trump hatchet men coming in to do heinous things to the Department of Defense, which couldnt be further from the truth,” Miller said.

The former top Trump administration official noted that the political climate leading up to the riot was a “constant drumbeat” of claims about “potential illegal, immoral, and unethical activities.”

During the speech Trump gave on the morning of Jan. 6, he incorrectly stated that the election had been stolen and that widespread voter fraud had occurred.

We fight like hell. And if you dont fight like hell, youre not going to have a country anymore, Trump said during the speech.

After his speech ended, pro-Trump rioters broke into the U.S. Capitol, causing lawmakers to flee or shelter in place. Five people died amid the riot, including one Capitol police officer.

Other Cabinet members at the time, including Transportation Secretary Elaine ChaoElaine ChaoDozens of Trump appointees ‘burrow’ into Biden governmentPolitical land mines await Garland at DOJIs nonpartisan effectiveness still possible?MORE and Education Secretary Betsy DeVosBetsy DeVosBiden orders review of Trump-era rule on campus sexual misconductDeVos’s student aid chief resigns from Education DepartmentCardona seeks to pivot from DeVos era at EducationMORE, resigned in response to the riot. DeVos directly cited Trump’s “rhetoric” and its effect on the rioters as reason for her resignation.

Miller’s full interview is set to air on Showtime at 8 p.m. on Sunday.