Military aircraft designed to drop bombs on surface targets. Aerial bombardment can be traced to the Italo-Turkish War (1911), in which an Italian pilot dropped grenades on two Turkish targets. In World War I zeppelins and large two- to four-engined biplanes were used as strategic bombers. In the 1930s small dive bombers were developed; they caused great destruction and panic in the Spanish Civil War and early in World War II. The latter conflict saw further development of heavy strategic bombers, which were used to destroy targets in the enemy's home territory; meanwhile, smaller fighter-bombers supported ground troops on the battlefield. After the war, jet-propelled long-range bombers carrying nuclear bombs were important to Cold War strategy, and they also dropped conventional bombs during the Vietnam War, the Persian Gulf War, and the Afghan conflicts. Efforts to evade increasingly sophisticated electronic early-warning systems have culminated in the development of U.S. stealth bombers, but cheaper and smaller jet fighter-bombers, equipped with electronic sensors and guided smart bombs, have proved effective in conflicts ranging from the Balkans to the Middle East.