President Trump’s abrupt announcement of an immediate U.S. troop withdrawal from Syria, along with indications he wants a significant drawdown in Afghanistan — decisions that bucked the advice of senior advisers, upended his administration’s own strategy, shocked U.S. allies and led to the resignation of his defense secretary — mark the full emergence of the foreign-policy president he always said he would be.

Over the past two years, as promised, Trump has canceled international climate and arms-control agreements and shattered trade accords. He has insulted traditional friends and fawned over adversaries.

But despite threatening to withdraw U.S. military forces from virtually every long-term deployment in the world, from South Korea and Japan to Germany and Iraq, as well as Syria and Afghanistan, Trump has been repeatedly constrained by the counsel of his own revolving-door national security team.

Until now. If there is a Trump Doctrine, the Syria withdrawal has brought it to full flower. As Trump himself tweeted Thursday morning, it should have been “no surprise. I’ve been campaigning on it for years.”

Trump’s turning that particular promise into reality was the final straw for Defense Secretary Jim Mattis. In his resignation letter to the president Thursday, Mattis said Trump deserved someone “whose views are better aligned with yours.” Others involved in Syria and Afghanistan policy are also expected to make early departures.

If he really wanted to scale back military involvement overseas, Trump could have chosen a much more prominent first example to make up for what he described as “getting NOTHING but spending precious lives and trillions of dollars protecting others.”

Deployments elsewhere are far larger and more expensive, and combat in other places has been far more lethal for Americans. About 2,000 U.S. troops are in Syria in any given moment. Over the three-year deployment, four U.S. service members have died — two combat and two noncombat deaths, according to the Pentagon. Tens of thousands of U.S. military personnel are stationed in the Far East and Europe; 14,000 are in Afghanistan.

And rather than getting nothing, administration officials have constantly credited the Syria deployment with protecting Americans, from terrorist attacks plotted by the Islamic State, and militant spinoffs across Asia and Africa. Touting its international leadership, the administration has taken credit for heading the coalition of dozens of countries, first set up by the Obama administration, against the Islamic State.

The Syria withdrawal also comes at a moment when the administration’s policy there — at least the one announced late last summer by his national security team — finally seemed to be paying off. The Islamic State’s physical caliphate in Syria and Iraq has been destroyed, although the group is far from “defeated,” as Trump has claimed. Senior administration officials had expected final conventional battles in southern Syria to last into next year, and tens of thousands of militants are said to be biding their time in Syrian and Iraqi towns and villages.

A second prong of the three-part strategy, the United Nations push for a political solution to the Syrian civil war that sparked the Islamic State’s rise in the first place, has finally been making progress. And, according to senior administration officials who declined to discuss anything in this week’s policy maelstrom other than anonymously, Iran — pressured by U.S. sanctions — has started to withdraw some of its Syria-based forces.

No one knows what will happen to any of those initiatives now. Many fear a bloodbath, with Turkey invading to attack Syrian Kurds, the soon-to-be-abandoned U.S. allies in the anti-militant fight, a new wave of refugees and humanitarian disaster.

But even as Trump tweeted an announcement of Mattis’s resignation, Secretary of State Mike Pompeo — said to be equally unhappy about the Syria decision but much more attuned to Trump’s overall way of doing things — looked on the bright side.

“Oh, goodness,” Pompeo told a radio interviewer who asked Thursday about allied response to the withdrawal decision, “the U.S. efforts under President Trump in Syria have had extraordinary success. . . . Our allies know the United States will always be the world’s leader in fighting against terrorism around the world. We’ve done it for decades, and we will continue to be alongside them, making sure that not only is America safe, but the threat from terrorism around the world is diminished.”

Many still dismiss the level of thought behind Trump’s utterances. “The president doesn’t have a strategy or a doctrine. He just has rages,” said Stephen Sestanovich, senior fellow for Russia and Eurasian Studies at the Council on Foreign Relations.

But as his determination to build an anti-immigrant wall on the Mexican border at all costs has shown, Trump’s confidence in his instincts, and what he calls his “gut,” has never wavered. It is only in the case of Syria, and now Afghanistan and possibly other areas of deployment, that his advisers have mustered themselves to push back with repeated success.

“We should stay the hell out of Syria,” Trump tweeted in 2013, as Obama was weighing a U.S. intervention. WHAT WILL WE GET FOR OUR LIVES AND $ BILLIONS?ZERO”.

Although he seemed pleased by the accolades he received for a quick cruise missile attack against Syrian President Bashar al-Assad’s use of chemical weapons early in his administration — and even buckled to adviser entreaties to send a few hundred more troops — Trump never wavered in his determination to leave Syria and other parts of the world.

“We’ll be coming out of Syria, like, very soon,” he said last April. “Let other people take care of it now.”

Anyone listening carefully, and willing to take Trump at his word, would have heard him describe over and over again, in speeches, interviews and throwaway comments, his disdain for and disinterest in the traditional U.S. military and diplomatic role in the world.

“We’re rebuilding other countries while weakening our own,” he said in the first major foreign-policy speech of his 2016 campaign. “I am the only person running for the presidency who understands this, and this is a serious problem.”

Others have seen American leadership in the construction of a new, post-Cold War order to fight the rise of state sponsored and non-terrorism by building better states. “We have witnessed the arrival of a new era,” President George W. Bush said after U.S. forces invaded Iraq. “Today we have the greater power to free a nation by breaking a dangerous and aggressive regime.”

Both Bush and President Barack Obama, despite their differences on Iraq and many other matters, believed that the U.S. role in the world was to build more stable countries by spreading Western values, making the United States safe by making the world safer and more integrated.

Trump, from the start, was having none of that. The U.S. military must be the strongest in the world, he argued, not for the world’s sake, but for our own.

Over and over again, with few variations, he spelled out a doctrine of the proper role for U.S. forces — to intimidate anyone who directly threatened the United States, and mete out punishment when it was deserved.

“We don’t have big aims in the world” under Trump, Sestanovich said. “We just aim to be the biggest and most powerful, and nobody should mess with us.