President Donald Trump knows little history. But he can read a short take, so someone should slip him a copy of Dwight Eisenhower's brief note of June 5, 1944, on the eve of the largest seaborne assault in history, D-Day, with World War II at stake."The troops, the air and the Navy did all that Bravery and devotion to duty could do," the supreme allied commander wrote in a message he intended to deliver only if the Normandy invasion failed.