The combination of that weird summit in Alaska with Vladimir Putin and the only slightly less bizarre gathering of NATO leaders in Washington, was the latest reminder that U.S. President Donald Trump is a terrible negotiator, a true master of the “art of the giveaway.” He doesn’t prepare, doesn’t have subordinates lay the groundwork beforehand, and arrives at each meeting not knowing what he wants or where his red lines are. He has no strategy and isn’t interested in the details, so he just wings it. As we learned during his first term, when he wasted time on those irrelevant...