All 10 living former defense secretaries warned in an op-ed on Sunday against involving the military in election disputes and urged leaders at the Defense Department to facilitate a smooth transition with the incoming administration.

The op-ed, published by The Washington Post, was an extraordinary public statement from a group of officials who served presidents from both parties. Its signatories included President Donald Trump’s two Senate-confirmed defense secretaries, James N. Mattis and Mark T. Esper, as well as former Vice President Dick Cheney.

The former defense secretaries weighed in with one voice as Trump continues to make baseless claims about the election and refuses to recognize his defeat.

“Our elections have occurred,” they wrote. “Recounts and audits have been conducted. Appropriate challenges have been addressed by the courts. Governors have certified the results. And the Electoral College has voted. The time for questioning the results has passed; the time for the formal counting of the Electoral College votes, as prescribed in the Constitution and statute, has arrived.”

In the op-ed, the former secretaries said unequivocally that the military had no role to play in settling election-related controversies.

“Efforts to involve the U.S. armed forces in resolving election disputes would take us into dangerous, unlawful and unconstitutional territory,” they wrote. “Civilian and military officials who direct or carry out such measures would be accountable, including potentially facing criminal penalties, for the grave consequences of their actions on our republic.”

The former defense secretaries also called for cooperation at the Pentagon during the transition between administrations, an issue that President-elect Joe Biden has complained about. Last week, Biden said his transition team had faced “obstruction” from the Defense Department.

In the op-ed, the former defense secretaries noted that transitions “can be a moment when the nation is vulnerable to actions by adversaries seeking to take advantage of the situation,” and they said it was critical that the transition at the Pentagon “be carried out fully, cooperatively and transparently.”