Is Mattis’ resignation the beginning of the end of America’s endless wars?

President Trump’s sudden decision this week to withdraw all U.S. troops from Syria and up to half the 14,000 U.S. forces from the war in Afghanistan shocked Washington — but it probably shouldn’t have.

Trump, in his own chaotic way, was doing what he had long vowed to do: end or at least sharply limit America’s endless wars in the post-9/11 age and bring American troops home.

Lawmakers and foreign leaders called the plans rash and misguided, warning that a broad U.S. retreat could create new instability in an unstable world and raise doubts about America’s military commitments.

Defense Secretary James N. Mattis was so furious that Trump would abandon allies in Syria and Afghanistan that he resigned in protest, telling the president that he needed a Pentagon chief whose “views are better aligned with yours.”

After two years of deferring to Mattis and other advisors who urged him to stay the course in far-flung wars, Trump acted on his own instincts to curtail the U.S. military reach and let local forces — or at least non-American forces — battle it out on their own.

Indeed, in addition to pulling all 2,000 troops out of Syria, Trump has told advisors that he wants to terminate the U.S. air war against Islamic State targets, a campaign of airstrikes that has raged since 2014.

If he proceeds, it could mark a major shift in the U.S. security posture and a major — but risky — achievement for Trump, one that eluded President Obama, who won the presidency twice in part by vowing to curb U.S. involvement in Iraq and Afghanistan.

Trump’s decision to pull troops out “fits a pattern, and it shouldn’t be surprising,” said Ivo Daalder, president of the Chicago Council on Global Affairs and a former Obama administration official. “Trump has said he would since the day he ran for president.”

Now that Trump has broken free of his advisors once, he might be tempted to go even further, cutting support for NATO, already a target of criticism, or withdrawing the 28,000 U.S. troops from South Korea. Congress almost certainly would seek to stop those moves, however.

In a video released by the White House, Trump said he could pull all U.S. forces from Syria because the U.S. and its allies had defeated Islamic State, the goal set after the militants first emerged and swept into neighboring Iraq in 2014, capturing vast swaths of territory.

But Trump’s declaration of victory could end up as fleeting as President George W. Bush’s televised rally aboard an aircraft carrier with a “Mission Accomplished” banner behind him shortly before the insurgency in Iraq broke out, plunging the country into violence that has not ended.

While Islamic State has lost its territory, thousands of fighters and supporters remain in eastern Syria, according to U.S. experts. Military commanders warn that the group could rebuild itself after U.S. troops pull out, again threatening Iraq and launching terrorist attacks in Europe and beyond.

Beyond that danger, the departure of U.S. troops will leave a power vacuum in northern Syria that other countries will inevitably fill. Syrian President Bashar Assad’s forces, backed by Russia and Iran, are most likely to surge forward, giving Moscow and Tehran greater sway over the region.

But the U.S. departure also leaves Syrian Kurdish fighters, who long operated as the Pentagon’s proxy ground forces against Islamic State, open to attacks from Turkish troops who view the Kurdish militias as allied with an insurgent group back home.

Trump has shown no indication that he is concerned about those or other dangers. But even he might not be able to quickly shrink America’s military role in wars that have defied easy exits.

Trump “makes bold statements and then retreats under pressure,” said Andrew Bacevich, a retired Army officer and a professor at Boston University who has long criticized U.S. military involvement.

“Establishment opposition to withdrawing troops from Syria and Afghanistan is already intense,” he said. “It remains to be seen whether in this instance Trump will stand firm and follow through.”

Trump’s announcement caught members of Congress from both parties off guard. Neither Kurdish leaders in Syria nor senior government officials in Afghanistan had advance notice.

Major U.S. allies in Europe also were not warned about the planned withdrawal, even though many of them have forces on the ground assisting U.S. forces in Syria and Afghanistan.

“The abrupt decision by the USA to pull its troops out of Syria is surprising not only to us,” Germany’s foreign minister, Heiko Maas, wrote on Twitter. Islamic State “has been pushed back but the threat is still there. There is a danger that this decision will damage the fight … and jeopardize the success achieved so far.”

In Israel, headlines Friday focused on Mattis’ cancellation of a planned visit next week that was supposed to focus on Syria and Iran. Analysts argued that the withdrawal from Syria left Israel more exposed to attacks from Iranian-backed groups.

Government officials “have tried to downplay the damage to Israel’s national security — but the defense establishment is up in arms,” analyst Chemi Shalev wrote in the Israeli newspaper Haaretz.

Against his own instincts, Trump deepened U.S. military involvement in the Middle East shortly after he took office in 2017, sending more U.S. troops into Syria to fight Islamic State, whose fighters had retreated there from Iraq.

U.S. forces also stepped up airstrikes and military assistance in Somalia, Libya, Yemen and several other countries in Africa against offshoots of Al Qaeda, Islamic State and an ever-widening stew of affiliated militant groups.

At Mattis’ urging, Trump accepted a Pentagon recommendation to send more than 9,000 military personnel back to Afghanistan as the government struggled to beat back a resurgent Taliban in a war that began 17 years ago.

A major U.S. drawdown now might suggest that Trump is on the verge of pulling out completely, encouraging the Taliban to fight on and dooming hopes of drawing it into peace talks aimed at a political solution, analysts said.

“It’s a good thing to come out of Afghanistan,” said retired Gen. Wesley K. Clark, a former top U.S. commander at the North Atlantic Treaty Organization. “But it’s perilous to come out this way and it reflects a lack of appreciation by the president for allies.”

But Trump never appeared comfortable with the direction Mattis and other members of his national security team took him. At times, he seemed at war with his own advisors.

In September, John Bolton, Trump’s national security advisor, told a Washington think tank that U.S. troops would stay in Syria until Iran removed its troops from the country. Trump has never given any indication he favored such an expanded mission.

Even lawmakers who give Trump credit for trying to end America’s endless wars are not optimistic he can carry it off without damaging U.S. credibility and harming or abandoning allies that U.S. troops have spent years defending.

“Trump’s instincts on non-intervention and not getting bogged down in the Middle East are actually better than many of his advisors,” said Rep. Ro Khanna, (D-Fremont.) “My fear is that he will do it in a way that will jeopardize lives in those places and our alliances.”

Many Trump supporters share his isolationist views against military involvement overseas. But a recent poll suggested that such views are in a clear minority.

In a survey last month, the nonpartisan Pew Research Center found that just 30% of U.S. adults said “reducing military commitments overseas” should be a top foreign policy priority, including just 26% of self-described Republicans and 34% of Democrats. In contrast, 66% of adults said “improving relationships with allies” should be a priority.

Times correspondents Erik Kirschbaum in Berlin and Noga Tarnopolsky in Jerusalem contributed to this story.

david.cloud@latimes.com

Twitter: @davidcloudLAT