If these allies come through, then the total western force could reach as many as 1,000 or 1,500 troops — creating an even more effective deterrent shield and leaving ISIS with less ability to recreate safe havens. Critically, it will help prevent Russia, Iran, and the Assad regime from gaining more power at the expense of American credibility and influence.

Advocates of American withdrawal sometimes fail to understand how few troops it often takes to secure American gains — or at least to prevent catastrophic losses. When Obama decided to pull out all American troops in Iraq, for example, he was deciding against leaving a relatively small force behind (small certainly compared to the large deployments at the height of the Iraq War), but it was a force more than strong enough to stop the ISIS blitzkrieg in 2014.

If Trump’s 200 can reassure American allies, incentivize allied deployments, and help keep a military boot on ISIS’s neck, then it will be one of the more cost-effective and wise decisions of his presidency. Trump’s mercurial nature is often a liability. When he changes his mind to reverse a mistake, it’s an asset. Let’s hope he doesn’t change his mind again.