While Washington should never leave American troops in harm’s way a day longer than national security interests require, President Donald Trump’s decision to pull back or withdraw U.S. troops from the Syrian border is morally wrong and strategically short-sighted.

His decision is wrong because the Syrian Democratic Forces (SDF), which include a significant contingent of Kurds, have courageously fought alongside the U.S. to dismantle ISIS’s so-called “caliphate.” Turkish strongman Recep Tayyip Erdogan wants to crush the SDF due to longstanding concerns regarding the Kurds. By pulling U.S. troops back from the Syrian border or withdrawing the troops altogether, Trump is giving Erdogan a green light to attack the SDF.

The SDF has taken heavy losses in the fight against ISIS because the U.S. mainly provided the air power, while the SDF provided the ground forces. Gen. Joseph Votel, who recently retired after serving as the top U.S. commander in the Middle East, said: “The SDF have been exceptional partners.” He estimated the group suffered nearly 11,000 casualties in the fight against ISIS. While ISIS and its ideology are not defeated, the SDF’s sacrifices likely spared the U.S. the need to deploy tens of thousands of ground troops.

Before Trump’s withdrawal announcement, the administration demanded that the SDF remove defensive barriers, leaving the SDF vulnerable to an impending Turkish intervention. The SDF dismantled its fortifications because it trusted the U.S. to restrain Turkey diplomatically. That promise now looks increasingly hollow.

Trump’s withdrawal decision is strategically short-sighted, because it will damage America’s reputation as a trustworthy ally across the globe. Diplomats from Russia, Iran, and China will have a new talking point as they whisper around the world that this is how Washington treats its friends. Fence-sitters will think twice before working with the U.S., tempted instead to bandwagon with America’s adversaries.

As a result, whether in the Middle East or in the global great power competition, America will find it more difficult to assemble coalitions to confront shared threats. That will mean letting threats grow worse or putting more American service members in harm’s way to compensate for the partners we can’t muster. President Trump’s impulse to abandon U.S. partners will therefore have the net effect of less security for Americans and more U.S. troops eventually deployed abroad without the help of allies and partners.

Trump appears to believe that if Washington would simply bring U.S. troops home and let other countries fend for themselves, then problems will go away on their own. If only it worked that way.

And Trump is not alone in this misperception. In town halls and presidential debates, as well as in Capitol Hill hearing rooms, a growing chorus of politicians employ impassioned and seductive arguments that begin and end with scornful references to “forever wars” or “endless wars.”

Isolationists and skeptics of America’s commitments overseas often quote John Quincy Adams’ 1821 admonition that America avoid going “abroad in search of monsters to destroy.” The United States should instead be the “well-wisher to the freedom and independence of all [but] the champion and vindicator only of her own,” Adams warned.

Compelling advice, indeed, that represented just what a new and weak nation enjoying uniquely advantageous geography needed to hear in the 19th century.

Unfortunately, that advice is less sound in a world that includes, for example, the internet, airplanes, weapons of mass destruction, and the ability of a few terrorists to kill thousands of people. Today, if we fail to deter and defeat the monsters overseas, they can and will kill us here — as Sept. 11, 2001, made painfully apparent.

But the threats are too numerous and our resources too limited to do it by ourselves. To simultaneously address persistent terror threats in the Middle East and compete more effectively with China and Russia, the U.S. needs friends, allies and partners.

That’s why Trump’s Syria withdrawal decision is so damaging and strategically short-sighted. It reinforces the narrative that America is an unreliable security partner, which makes others less likely to work with the U.S. when we need them.

Rather than an endless war waged in the name of nation-building and regime change, the U.S. mission in Syria is actually a powerful example of how we can defeat terrorists without deploying 100,000 troops or more. Instead, the U.S. deployed a relatively small number of troops in support of partners numbering in the tens of thousands.

As the Syrian example suggests, the U.S. can pursue key objectives with small, shrewdly designed forward deployments that empower regional partners to further shared objectives and fight common enemies. This is an application of the military principle known as “economy of force” — put simply, the idea of doing as much as possible with less so that other priorities can be simultaneously pursued.

Unfortunately, to the detriment of U.S. national security, that kind of mission is exactly what Trump is trying to end in Syria. He should change his mind before it’s too late.

Bradley Bowman is senior director of the Center on Military and Political Power at the Foundation for Defense of Democracies, a Washington-based nonpartisan research institute focusing on national security and foreign policy.

Editor’s note: This is an Op-Ed and as such, the opinions expressed are those of the author. If you would like to respond, or have an editorial of your own you would like to submit, please contact Military Times managing editor Howard Altman, haltman@militarytimes.com.