American commandos were working alongside Kurdish forces at an outpost in eastern Syria last year when they were attacked by columns of Syrian government tanks and hundreds of troops, including Russian mercenaries. In the next hours, the Americans threw the Pentagon’s arsenal at them, including B-52 strategic bombers. The attack was stopped.

That operation, in the middle of the American-led campaign against the Islamic State in Syria, showed the extent to which the United States military was willing to protect the Syrian Kurds, its main ally on the ground.

But now, with the White House revoking protection for these Kurdish fighters, some of the Special Forces officers who battled alongside the Kurds say they feel deep remorse at orders to abandon their allies.