The bombing of strategic targets from the air dates back to the beginning of World War I, when the Germans used zeppelins to bomb Paris and London. By the end of the war, planes were being designed specifically as bombers. The first new type to gain prominence was the dive bomber, which makes a steep dive toward the target before releasing its bombs. In Germany's invasions of Poland and France early in World War II, the Stuka dive bomber opened the way for German armoured columns by shattering enemy ground defenses and terrorizing civilians. The Stuka was designed to employ the dive-bombing technique developed earlier by the U.S. Navy, i.e., diving vertically at a target, releasing the bombs while still in a dive, and only then pulling out into straight flight to get away. The Stuka had dive brakes to slow the dive and give the pilot more time to aim his airplane and, thereby, the bomb. The scream of the diving airplane terrified people on the ground, and this effect was enhanced by the addition of cardboard sirens both to the airplanes and to their bomb load. Although the Stukas, refined from time to time, were used throughout the war, their maximum speed was just 210 miles per hour (335 km per hour), and they proved no match for the British combination of early warning by radar and fast fighter planes.