WASHINGTON — President Trump’s decision to withdraw all U.S. forces from Syria is already having unintended consequences. The U.S. departure could lead to the release of 1,100 Islamic State fighters now held in detention camps in northeastern Syria — creating a dangerous new terrorist threat to the West.

The Syrian Democratic Forces (SDF) — the Kurdish and Arab proxy forces whom the United States armed and trained to fight the Islamic State — do not have the capacity to guard and feed so many terrorists without U.S. support. And The Post reports that their home countries “are refusing to repatriate their citizens, citing the risk that they would spread radical ideology or perhaps carry out attacks back home.” If the SDF is abandoned by its U.S. patrons, it might have no choice but to release them.

How much damage could these terrorists cause? To put it in perspective, the Islamic State had only about 700 fighters left when President Barack Obama withdrew U.S. forces from Iraq in 2011 — yet from that tiny nucleus, the Islamic State grew into the world’s largest, most powerful terrorist network, until Trump unleashed our military to beat the group back. Imagine what destruction an influx of 1,100 terrorists into the global ecosystem could wreak. The Islamic State detainees hail from 32 countries, including many believed to be from Europe.

The optimal solution would be for Trump to reconsider his withdrawal plan so that we can keep these detainees in Syria under the watchful eye of U.S. intelligence and Special Operations forces. But there is also another possible solution — one that would help the president keep another campaign promise:

Send them to Guantanamo Bay.

In January, President Trump issued an executive order that authorized the U.S. military and intelligence community to “transport additional detainees to U.S. Naval Station Guantanamo Bay when lawful and necessary to protect the Nation.” During his State of the Union address, Trump asked Congress “to ensure that, in the fight against ISIS and al-Qaida, we continue to have all the necessary power to detain terrorists — wherever we chase them down, wherever we find them. And in many cases for them it will now be Guantanamo Bay.” In March, Congress responded by approving more than $200 million in new construction for Guantanamo Bay as part of the omnibus spending bill. And this spring, the Pentagon formally authorized the station to receive new detainees who pose a “continuing, significant threat.”

There is little doubt that a number of the Islamic State fighters now held in Syria would make excellent candidates for detention at Guantanamo Bay. Trump should order the intelligence community to conduct a threat assessment for each of the detainees to see which ones would qualify for transfer. No doubt, a decision to move some of the prisoners from Syria to Guantanamo would create an uproar in Europe — particularly from countries whose citizens would be transferred. These would be the very same countries currently refusing to take custody of their citizens who went to fight for the Islamic State. Trump should give any complaining countries an ultimatum: Either take your nationals back, or they are headed to Guantanamo.

Transfer to Guantanamo is a less than optimal solution, because right now high-value detainees held on the battlefield in Syria do not have access to lawyers and cannot challenge their detentions in court — which means they can be effectively interrogated for intelligence purposes. But once transferred to Guantanamo, they would immediately get lawyers and the right of habeas corpus — which dramatically reduces their intelligence value.

Instead of transferring these terrorists, we should keep them where they are — and continue supporting the SDF until the estimated 30,000 Islamic State fighters still at large in Iraq or Syria are all killed or captured. The Islamic State is not defeated — not by a long shot.

But this much is clear: We cannot allow more than a thousand dangerous terrorists to be released into the world so that they can return to the fight. They must be kept off the battlefield. Better to keep them in Syria than in Guantanamo, to be sure.

But better to keep them in Guantanamo than release them to carry out jihad against the West.

Marc A. Thiessen is a columnist with The Washington Post. Follow him on Twitter,  @marcthiessen.

Marc Thiessen