Ukraine’s stunning success with drones in the Black Sea, sinking or heavily damaging an estimated 30 Russian naval vessels in more than three years of war, has not gone unnoticed in the U.S. Drones have become a priority at the Pentagon. The Defense Advanced Research Projects Agency this month christened the USX-1 Defiant, a first-of-its-kind autonomous unmanned surface vehicle designed from the ground up for deployment in the sea without a human crew. The 180-foot, 240-metric-ton...