Local Syrian forces have captured and turned over to the U.S. military an unnamed American citizen fighting for the Islamic State (ISIS), the Pentagon announced Thursday.

“Syrian Democratic Forces turned over an American citizen who surrendered to SDF on or around Sept. 12 to U.S. forces,” a Pentagon spokesman said, according to the Washington Post. “The U.S. citizen is being legally detained by Department of Defense personnel as a known enemy combatant.”

The Post reported that the ISIS fighter was not identified, nor were any details released of how he surrendered.

While Americans traveling to join ISIS is relatively uncommon, with the Post reporting that 44 of approximately 200 who attempted to reach ISIS territory succeeded, this is not the first capture of an American citizen.

In March 2016, Mohamad Jamal Khweis of Virginia was captured by Kurdish forces in Iraq after he changed his mind and fled Mosul. The 27-year-old was believed to be the first American captured on the battlefield charged with joining ISIS.

CNN reports that, with increasing defeats for the Islamic terror group, more fighters are surrendering to the SDF in Syria.

The SDF is a U.S.-backed Kurdish-Arab coalition that has been recently pushing into Raqqa — the de facto capital of ISIS.

The Post reports that as many as 40,000 foreign fighters have traveled to Iraq and Syria to join ISIS — predominantly from the Middle East and Africa, but significant numbers from Europe as well.

Seamus Hughes of the George Washington University Program on Extremism told NBC News that the fighter could be valuable for intelligence.

“You’re looking at a man who was there to the bitter end,” Hughes said. “Would he have insight on whether they’re sending folks away from Iraq and Syria in a systematic way? Are they hunkering down?”

Adam Shaw is a Breitbart News politics reporter based in New York. Follow Adam on Twitter: @AdamShawNY.