Former Navy SEAL commander William McRaven says US under attack from Trump In an op-ed, he said the 'fate of our Republic' depends on a new president.

The retired Navy admiral who oversaw the mission that killed Osama bin Laden rebuked President Donald Trump for what he called the abandonment American leadership domestically and abroad in an op-ed, citing what he said he'd heard from members of the military and intelligence community.

“The America that they believed in was under attack, not from without, but from within,” Adm. William H. McRaven, who led the U.S. Special Operations Command before retiring, wrote in the New York Times Thursday describing the mood at two functions he attended in the span of a week -- one at an Army change of command ceremony and the other a gala honoring members of the intelligence and Special Operations communities.

Recalling a conversation he had while attending a ceremony at Fort Bragg in North Carolina, McRaven wrote, “one retired four-star general, grabbed my arm, shook me and shouted, ‘I don’t like the Democrats, but Trump is destroying the Republic!’”

McRaven castigated Trump for what he described as failing to stand up to tyrannical regimes abroad and assaulting U.S. institutions, behavior that he said undermines the nation’s standing in the world, and said “it is time for a new person in the Oval Office” if “this president doesn’t demonstrate the leadership that America needs.”

McRaven’s comments come just over a week after Trump announced his decision to withdraw U.S. troops from Syria -- leaving America’s Kurdish partners to fend for themselves against Turkey and the Assad regime -- and amid an impeachment inquiry that is ensnaring a growing list of Trump administration officials and associates.

Vice President Mike Pence has since traveled to Turkey in an attempt to curb Turkey’s operation, and acting Chief of Staff Mick Mulvaney on Thursday admitted to ABC News Chief White House Correspondent Jon Karl that the administration withheld military aid in part to pressure Ukraine to launch an investigation into political opponents.

Thursday’s op-ed is not the first time McRaven has criticized the president. Last year, in an op-ed published in the Washington Post shortly after CIA director John Brennan’s security clearance was revoked, McRaven wrote that Trump “embarrassed us in the eyes of our children, humiliated us on the world stage and, worst of all, divided us as a nation.”

Trump dismissed those comments at the time, calling McRaven a “Hillary Clinton backer and an Obama backer” in a Fox News interview, though McRaven later told CNN that he “did not back Hillary Clinton or anyone else.”

McRaven's op-ed was published on the same day that Trump's former defense secretary, retired Gen. James Mattis, took a few jabs of his own at Trump. At a white-tie dinner in New York, just a day after Trump called Mattis “the world’s most overrated general,” Mattis said, "I'm honored to be called that by Donald Trump, because he also called Meryl Streep an overrated actor. So I guess I’m the Meryl Streep of generals."