American troops mount an anti-aircraft gun near the Algerian coastline in 1943

Anti-aircraft warfare, or air defense, is any method of engaging hostile military aircraft in defense of ground objectives, ground or naval forces or denial of passage through a specific airspace region, area or anti-aircraft combat zone[1]. It is also used in denying entry into national air space to unauthorized aircraft.

From the initial introduction of aircraft into combat during the First World War the means to achieve air defense included infantry firearms, light anti-aircraft weapons, cannons and anti-aircraft artillery as well as barrage balloons and Interceptor aircraft, with all, aided by radar installations, growing in power and accuracy over the course of the 20th century, particularly with the introduction of the surface-to-air missile to self-propelled anti-aircraft weapons.