war, 54 airship raids had been undertaken, in which 557 people were killed and 1,358 injured. Of the 80 airships used by the Germans in World War I, 34 were shot down and further 33 were destroyed by accidents. 389 crewmen died. The Zeppelin raids were complemented by the Gotha G bombers from 1917, which were the first heavier than air bombers to be used for strategic bombing, and by a small force of five Zeppelin-Staaken R.VI "giant" four engined bombers from late September 1917 through to mid-May 1918. Twenty-four Gotha twin-engined bombers were shot down on the raids over England, with no losses for the Zeppelin-Staaken giants. Further 37 Gotha bombers crashed in accidents. They dropped 73 tons of bombs, killing 857 people and wounding 2058. It has been argued that the raids were effective far beyond material damage in diverting and hampering wartime production, and diverting twelve squadrons and over 17,000 men to air defenses. Calculations performed on the number of dead to the weight of bombs dropped had a profound effect on attitudes of the British government and population in the interwar years, who believed that "The bomber will always get through". Observation balloons Manned observation balloons floating high above the trenches were used as stationary reconnaissance points on the front lines, reporting enemy troop positions and directing artillery fire. Balloons commonly had a crew of two equipped with parachutes: upon an enemy air attack on the flammable balloon, the crew would parachute to safety. Recognized for their value as observer platforms, observation balloons were important targets of enemy aircraft. To defend against air attack, they were heavily protected by large concentrations of antiaircraft guns and patrolled by friendly aircraft. Blimps and balloons helped contribute to the stalemate of the trench warfare of World War I, and contributed to air-to-air combat for air superiority because of their significant reconnaissance value. To encourage pilots to attack enemy balloons, both sides counted downing an enemy balloon as an "air-to-air" kill, with the same value as shooting down an enemy aircraft. Some pilots, known as balloon busters, became particularly distinguished by their prowess at shooting down enemy balloons. The premier balloon busting ace was Willy Coppens: 35 of his 37 victories were enemy balloons. Leading aces As pioneer aviators invented air-to-air combat, the contending sides developed various methods of tracking aerial casualties and victories. Aviators with five or more aerial