With the end of their convention, the Republican Party and Donald Trump have reached what in military theory is called the “culminating point.” “The culminating point of victory,” according to the Modern War Institute at West Point, “is the threshold when military advantages peak and then rapidly turn into disadvantages.” As an infantryman, I was taught that the culminating point is a paradox; it’s a moment of maximum vulnerability at a time when you believe you are at maximum strength. Let’s say your platoon has just taken a hill. Exhausted and jubilant, you’ve achieved your objective. Your troops have sent...