When Hitler's armies occupied Italy in 1943, they also seized control of mankind's greatest cultural treasures. As they had done throughout Europe, the Nazis could now plunder the masterpieces of the Renaissance, the treasures of the Vatican, and the antiquities of the Roman Empire. On the eve of the Allied invasion, General Dwight Eisenhower empowered a new kind of soldier to protect these historic riches. In May 1944 two unlikely American heroes--artist...