Under investigation for impeachment he may be, but President Trump can still shake the world with his tweets. Explaining his decision to pull U.S. troops away from the Turkish-Syrian border at the cost of the Kurdish-led Syrian Democratic Forces, and open the way for Turkish forces to create what Ankara calls a “safety zone,” President Trump tweeted early Monday that “it is time for us to get out of these ridiculous Endless Wars, many of them tribal, and bring our soldiers home.”

Hitting the caps-lock button, Mr. Trump went...