If Donald Trump pulls U.S. troops out of Syria so that troops of our ally Turkey can march in unobstructed and slaughter the fighters of our Kurdish allies, it will be the greatest betrayal perpetrated by the United States in its history: a betrayal not only of the Kurdish fighters who have done so much of our dirty work in both Syria and Iraq, but of our most cherished beliefs about ourselves. We will never live down the deserved shame that we will earn.