President Trump has made a fateful and terrible decision in announcing that the United States will abandon the Kurds in northeastern Syria to the mercies of Turkey’s autocratic leader, Recep Tayyip Erdoğan.

Trump’s betrayal leaves our Kurdish allies open to the possibility, nay likelihood, of mass killings. It also sets up conditions for a wider geopolitical disaster. The winners are Turkey, Russia, Syria, Iran, and the Islamic State. The biggest loser, after the Kurds, is the U.S.