Syria represents a test of President Trump’s foreign policy leadership. Although the Trump administration had originally planned on keeping U.S. troops in Syria indefinitely, last week Trump surprised his own security advisers, telling them that he wants ISIS defeated and a full withdrawal by 2018, ordering the State Department to suspend $200 million in recovery and humanitarian assistance to Syria, and telling reporters that the troops would be pulling out of Syria “very soon.”

If recent American experience is any guide, however, the United States will wind up stuck in Syria despite Trump’s instincts and best efforts. Now, after another chemical weapon attack, the United States may even find itself escalating its efforts in Syria.

Trump is correct to want a speedy withdrawal. The Islamic State in Syria has been rousted from its physical “caliphate” and its remnants are on the run. Syria’s civil war still rages and there is no real chance for the United States to shape the political future of Assad or of Syria. Meanwhile the probability of deadly encounters with Russia, Iran and even Turkey remains very high for the foreseeable future. In short, the risks and costs of military intervention in Syria at this point far outweigh the benefits.

Nonetheless, America’s track record of foreign intervention since 9/11 makes it clear that leaving is easy to wish but hard to do. Presidents seeking to withdraw from interventions must always confront those who argue that it is the wrong time to leave. There is always another crisis to manage, always another danger likely to emerge if the United States were to withdraw right now. Though clearly there are situations that call for perseverance, American leaders must recognize when the costs of trying to reduce risk outweigh the benefits.

Although it is theoretically possible that a small group of people in Afghanistan, Iraq or Syria will launch a terrorist attack against the United States in the future, that risk is very low and the costs of endless intervention and nation-building are very high. The inability to recognize the tipping point is how “mission accomplished” in Afghanistan and Iraq turned into a war on terror with no end in sight.

The news this week of more suspected chemical weapons attacks in Syria is a perfect example of this dynamic. The immediate impact of the crisis has been to embolden advocates of American intervention (like Senator John McCain), encouraging them not only to criticize Trump for wanting to withdraw and also to call for yet more intervention. Having already punished Assad once before in response to the use of chemical weapons, Trump will certainly feel pressure to retaliate in light of such criticism. But if Trump does launch another strike, he will only strengthen the presumption that the United States should be responsible for events in Syria. This will, in turn, make leaving Syria even more difficult.

The situation in Syria also reflects a more general pattern of mission creep. In Afghanistan, the desire to hunt down and destroy Al Qaeda morphed into regime change and from there into a full-blown nation-building effort. The invasion of Iraq shifted began with the removal of Saddam Hussein and ended up a long-running counterinsurgency and nation-building campaign. The 2011 intervention in Libya began as a move to stop the slaughter of civilians but quickly expanded into regime change and has now started to suck in the United States and its allies into yet another counterterrorism and political stability operation.

The United States has yet to withdraw fully from any of these places and the pattern suggests that the Trump administration will find other things to do in Syria. Though Trump has been clear that defeating the Islamic State was his goal, new objectives (and justifications) for American intervention in Syria have proliferated exponentially. Arguments for continued or expanded American efforts in Syria have included humanitarian concerns, concerns about Russian and Iranian influence, and concerns about the impacts of the conflict on Turkey, Israel and Saudi Arabia.

The strongest evidence that Trump will keep troops in Syria, however, is that he has already lost the same debate once before over Afghanistan. Despite Trump’s insistence, his national security team’s belief in the effectiveness of continued military intervention eventually convinced Trump to give in and agree to a surge in troop levels. It is possible that his new national security adviser, John Bolton, will tip the scales in the opposite direction, but recent history suggests we should expect a lengthy stay in Syria.