Retired Navy SEAL Adm. William McRaven declared in a blistering New York Times op-ed Thursday that America's institutions are "under attack" by President Trump, denouncing the precipitous withdrawal from Syria.

McRaven, the former head of U.S. Special Operations Command (SOCOM) who organized the 2011 raid that killed Al Qaeda leader Usama bin Laden, accused Trump of not understanding the importance of America's role in the world.

"And if this president doesn’t understand their importance, if this president doesn’t demonstrate the leadership that America needs, both domestically and abroad, then it is time for a new person in the Oval Office — Republican, Democrat or independent — the sooner, the better. The fate of our Republic depends upon it," he wrote, arguing U.S. allies will lose trust in the United States if promises are not kept.

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The op-ed was published just hours before Trump announced a cease-fire between Turkish and Kurdish-led forces in Syria.

Despite the announcement, journalists have reported continued fighting in the Syrian town of Ras al-Ayn on Friday morning, while other areas have reported relative calm since the agreement.

Journalists from the Associated Press reported witnessing shelling and said they could see smoke billowing around the town, which sits along the border with Turkey. The Syrian Observatory for Human Rights, a war monitor, reported intermittent clashes in Ras al-Ayn, but calm elsewhere.

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McRaven contrasted Trump's statements with recent military gatherings he's attended, including one honoring a young female sailor who was killed in Syria fighting ISIS. He explained that the woman's husband, a former Army Green Beret, accepted the award on his behalf.

"But, beneath the outward sense of hope and duty that I witnessed at these two events, there was an underlying current of frustration, humiliation, anger and fear that echoed across the sidelines. The America that they believed in was under attack, not from without, but from within," he wrote.

McRaven recalled that at Fort Bragg in North Carolina, a retired four-star general "grabbed my arm, shook me and shouted, 'I don’t like the Democrats, but Trump is destroying the Republic!'"