DOVER AIR FORCE BASE, Del. — President Donald Trump traveled Monday to Dover Air Force Base in Delaware to pay respects to two U.S. soldiers killed Saturday in Afghanistan when a soldier dressed in an Afghan army uniform opened fire with a machine gun. National security adviser Robert O’Brien told reporters traveling with Trump on Air Force One that the president wrapped up a reelection campaign rally in New Hampshire a bit early so he could visit with the families of the soldiers. He described such moments as “probably the toughest thing he does as president,” along with visiting wounded...