Condemnation of his stance was quick and severe, not only from Democrats but from Republicans who have been staunch Trump supporters on virtually all issues.
Esper isn't saying how many U.S. troops will leave the north, but he says they represent most of the 1,000 troops in Syria.
Turkey launched its offensive Wednesday against Kurdish fighters in Syria, who have helped the U.S. against the Islamic State.
Why has the U.S. pulled its troops and why is Turkey entering northern Syria? Here's a look at what's happening.