WASHINGTON — President Donald Trump isolated himself from top allies and advisers with his unilateral decision to withdraw U.S. forces from Syria, triggering a backlash in Washington and around the globe unlike any he has seen during past go-it-alone moves on foreign policy.

At a White House meeting Thursday, Defense Secretary James Mattis handed Trump a blunt resignation letter that pointed to the president's failure to work with long-standing U.S. partners — and his empowerment of U.S. adversaries — as reasons for his departure.

"My views on treating allies with respect and also being clear-eyed about both malign actors and strategic competitors are strongly held and informed by over four decades of immersion in these issues," Mattis wrote. "Because you have the right to have a Secretary of Defense whose views are better aligned with yours on these and other subjects, I believe it is right for me to step down from my position."

Mattis provided the most dramatic display of resistance to Trump's decision in Washington, but not the most histrionic. Capitol Hill unleashed its fury in barbed soundbites.

A fulminating phalanx of Republican hawks, led by onetime rival and now usually loyal ally Sen. Lindsey Graham of South Carolina, said that Trump is empowering Moscow, Tehran, Syrian leader Bashar al-Assad and the remnants of the Islamic State while abandoning U.S. allies in the region and around the world.

The withdrawal is "a stain on the honor of the United States," Graham said.

Centrist Democrats are echoing their talking points, and even war-weary liberals say Trump has imperiled national interests by rushing into a policy without a serious plan for pulling troops out and addressing the humanitarian crisis in Syria.

They all point to the approval Trump is getting from Russian President Vladimir Putin.

For some presidents, the lonely path in Washington would be an uncomfortable one. But to Trump, it's a sign that he's on the right track.

"I think it’s a healthy backlash because politicians aren’t popular, and when politicians attack Trump it allows him to position himself as something other than a politician," said a former Trump White House official who spoke on the condition of anonymity because he was not authorized to speak for the president.

When the Washington establishment is against Trump on an issue like Syria, this former White House official said, "it’s usually the opposite that’s happening around the rest of the country."

Perhaps the best measure of just how isolated Trump is on this policy in the nation's capital is the composition of the small set of lawmakers who are rallying around him, a group led by Sen. Rand Paul, R-Ky., whose opposition to foreign aid and U.S. military intervention has earned him the derision of the bipartisan Washington foreign policy and military establishment.

"I am happy to see a President who can declare victory and bring our troops out of a war," Paul tweeted Wednesday. "It’s been a long time since that has happened."

Critics of Trump's policy are quick to point out that the loss of physical territory has not ended the fight for ISIS forces.

Still, Rachel Bovard, policy director at the Conservative Partnership Institute and a former foreign policy aide to Paul, said it's a heady moment for the iconoclastic senator and his allies.

They have been frustrated in recent weeks because House Republican leaders used procedural maneuvers to prevent Rep. Thomas Massie, a Paul friend, from starting a floor debate on U.S. involvement in Yemen. Now, though the president has made a bold and somewhat unexpected stride in their direction on Syria.

"I don’t think that they saw this coming. He’s obviously grabbing onto it now," Bovard said. "I don’t think they’re working in concert. I don’t think Trump works in concert."

Trump and Paul are not entirely alone. Sen. Mike Lee, R-Utah, explained the logic behind his support for Trump's move in an interview with Fox's Shannon Bream Wednesday night.

"Congress has never declared war, or authorized the use of military force in Syria," he said. "We shouldn't be there anyway."

The Senate declined to vote on an authorization for the use of force in Syria in 2013 after President Barack Obama requested one. Two years later, Graham introduced a resolution that would have provided for an open-ended commitment of ground forces — with no limitation on duration or geography — to fight the Islamic State, but it was killed without debate or a vote.

Only now, after Trump declared his intention in a Wednesday tweet, have lawmakers been scrambling to assert themselves on Syria policy.

"It's a little bit rich from these people who don’t want to have a debate over it but then when Congress doesn’t have a say they flip out," Bovard said.

For the better part of a year, Trump has said publicly that he would pull troops out of Syria soon. So, while elected and appointed officials were surprised by the abruptly and publicly announced decision, they couldn't claim to have been ignorant of his intentions.

At a press conference Thursday, Graham urged Trump to reconsider.

"We have two choices to fight this war: in their backyard or our backyard," he said. "Mr. President, you have a chance to change course. You have a lot of bipartisan support to do so. Take advantage of it."

But for Graham, the problem is that Trump doesn't want to be aligned with the foreign policy consensus in Washington or around the world. He'd much rather stand alone.