Anti-aircraft artillery

It is almost impossible to score a direct hit on a high-flying airplane. The shells fired from anti-aircraft guns are set to explode near the enemy aircraft. In this way the fragments or pieces of the exploded shells will hit the enemy aircraft. The newest type of anti-aircraft weapon is not a gun but a rocket. A rocket is fired from the ground and controlled in its flight by radio. It is called a guided missile, because the radio or radar guides it to its target—the enemy aircraft. Anti-aircraft guns are placed all around a place that must be defended against air attack. They are grouped in batteries. A battery usually consists of four guns. As many as five hundred guns were fired at one time in defending cities during World War II.

Enemy bombers were often forced to fly through a thick hail of exploding shells. The airmen in World War II used two nicknames for anti-aircraft fire. The first name, "flak," came from the German word for antiaircraft. The second name, "ack-ack," came from the initials of anti-aircraft, and also the noise made by the firing of the guns.