Large NATO drills in the frigid fjords of northern Norway may be just war games meant to hone the fighting skills of the newly expanded 32-nation military alliance. But for troops taking part, they are very real. This week, crew members aboard the French frigate Normandie, one of France’s most modern warships, were roused from sleep and scrambled to hunt down and kill a submarine that snuck into cold Norwegian waters. The submarine belongs to Germany, also a NATO member. But for the purpose of the war games dubbed Nordic Response 2024, it was acting as an enemy vessel. The...