aa guns
Air defence is defined by as "all measures designed to nullify or reduce the effectiveness of hostile air action." They include ground-and air-based weapon systems, associated sensor systems, command and control arrangements and passive measures. It may be used to protect naval, ground, and air forces in any location. However, for most countries the main effort has tended to be 'homeland defence'. NATO refers to airborne air defence as counter-air and naval air defence as anti-aircraft warfare. Missile defence is an extension of air defences.