Air warfare played an integral role in World War II. This certainly wasn't the first use of aircraft in war, but it was the first war in which aircraft were used with such devastating effectiveness. Aircraft evolved dramatically between World War I and the onset of World War II in 1939. In the first war, before effective bombsights and standardized bomb fittings were developed, bombs were dropped by hand from the cockpit. During World War II, heavy bombers could rain bombs on targets, destroying several city blocks at a time. Fighter planes provided protection for bombers and attacked enemy planes, ships, and ground troops.