Autocannon in the context of Automatic firearm

Anti-aircraft warfare (AAW) or air defence (or air defense in American English) is the counter to aerial warfare and includes "all measures designed to nullify or reduce the effectiveness of hostile air action". It encompasses surface-based, subsurface (submarine-launched), and air-based weapon systems, in addition to associated sensor systems, command and control arrangements, and passive measures (e.g. barrage balloons). 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. Missile defence is an extension of air defence, as are initiatives to adapt air defence to the task of intercepting any projectile in flight.

Most modern anti-aircraft (AA) weapons systems are optimised for short-, medium-, or long-range air defence, although some systems may incorporate multiple weapons (such as both autocannons and surface-to-air missiles). 'Layered air defence' usually refers to multiple 'tiers' of air defence systems which, when combined, an airborne threat must penetrate to reach its target; this defence is usually accomplished via the combined use of systems optimised for either short-, medium-, or long-range air defence.

An infantry fighting vehicle (IFV), also known as a mechanized infantry combat vehicle (MICV), is a type of armoured fighting vehicle, light tank, and armoured personnel carrier used to carry infantry into battle and provide direct-fire support. The 1990 Treaty on Conventional Armed Forces in Europe defines an infantry fighting vehicle as "an armoured combat vehicle which is designed and equipped primarily to transport a combat infantry squad, and which is armed with an integral or organic cannon of at least 20 millimeters calibre and sometimes an antitank missile launcher". IFVs often serve both as the principal weapons system and as the mode of transport for a mechanized infantry unit.

Infantry fighting vehicles are distinct from general armored personnel carriers (APCs), which are transport vehicles armed only for self-defense and not specifically engineered to fight on their own. IFVs are designed to be more mobile than tanks and are equipped with a rapid-firing autocannon or a large conventional gun; they may include side ports for infantrymen to fire their personal weapons while on board.

Close air support (CAS) is defined as aerial warfare actions—often air-to-ground actions such as strafes or airstrikes—by military aircraft against hostile targets in close proximity to friendly forces. A form of fire support, CAS requires detailed integration of each air mission with fire and movement of all forces involved. CAS may be conducted using aerial bombs, glide bombs, missiles, rockets, autocannons, machine guns, and even directed-energy weapons such as lasers.

The requirement for detailed integration because of proximity, fires or movement is the determining factor. CAS may need to be conducted during shaping operations with special forces if the mission requires detailed integration with the fire and movement of those forces. A closely related subset of air interdiction, battlefield air interdiction, denotes interdiction against units with near-term effects on friendly units, but which does not require integration with friendly troop movements. CAS requires excellent coordination with ground forces, typically handled by specialists such as artillery observers, joint terminal attack controllers, and forward air controllers.

Saturation fire is a saturation attack using an intense level of artillery bombardment or rapid direct fire (from automatic weapons such as machine guns, autocannons or rotary guns) that is designed to overwhelm a target area with lethal firepower, for the purpose of suppression, area denial or mass destruction of the enemy.

Rifling is the term for helical grooves machined into the internal surface of a firearms's barrel for imparting a spin to a projectile to improve its aerodynamic stability and accuracy. It is also the term (as a verb) for creating such grooves. The opposite of rifling is smoothbore.

Rifling is measured in twist rate, the distance the rifling takes to complete one full revolution, expressed as a ratio with 1 as its base (e.g., 1:10 inches (25.4 cm)). A shorter distance/lower ratio indicates a faster twist, generating a higher spin rate (and greater projectile stability).

Fragmentation is the process by which the casing, shot, or other components of an anti-personnel weapon, bomb, barrel bomb, land mine, IED, artillery, mortar, tank gun, autocannon shell, rocket, missile, grenade, etc. are dispersed and/or shattered by the detonation of the explosive filler.

The correct term for those pieces is "fragments” (nicknamed “splinters” or “shards”). Preformed fragments can be of various shapes (spheres, cubes, rods, etc.) and sizes and are normally held rigidly within some form of matrix or body until the high explosive (HE) filling is detonated. The resulting high-velocity fragments produced by either method are the main lethal mechanisms of these weapons, rather than the heat or overpressure caused by detonation, although offensive grenades are often constructed without a frag matrix.

A machine gun (MG) is a fully automatic and rifled firearm designed for sustained direct fire. Automatic firearms of 20 mm (0.79 in) caliber or more are classified as autocannons rather than machine guns.

As a class of military kinetic projectile weapons, machine guns are designed to be mainly used as infantry support weapons and generally used when attached to a bipod or tripod, a fixed mount or a heavy weapons platform for stability against recoil. Many machine guns also use belt feeding and open bolt operation, features not normally found on other infantry firearms.

A weapons platform is generally any structure, vehicle or mechanism on which a weapon can be installed (via various mounting mechanisms) for optimal stability and performance. The mounted weapons, the platform and all other associated supporting equipments together form the weapon system.

In more general use, a weapons platform could be structured around a gun, such as a gun turret on a ship, or bracing on an aircraft. For example, a jet aircraft is a weapons platform for missiles, bombs or autocannons, and the resultant weapon system is the fighter jet; a motorboat can serve as a weapons platform for automatic weapons, torpedoes and flamethrowers, resulting in weapon systems such as gunboats and fast attack crafts. Land vehicles, either wheeled, tracked or mixed, are also considered weapons platforms for grenade launchers, machine guns, recoilless guns and some missile launchers, which transform the vehicles into weapon systems such as armored cars (such as the Humvee), IFVs and technicals (improvised from civilian pickup trucks). In addition, artificial satellites have been proposed as potential space weapon platforms. These satellites could carry an arsenal of weapons, such as to threaten other countries with the possibility of an orbital nuclear strike (see Rods from God).

Air-to-ground weaponry is aircraft ordnance used by combat aircraft to attack ground targets. The weapons include bombs, machine guns, autocannons, air-to-surface missiles, rockets, air-launched cruise missiles and grenade launchers.

A light bomber is a relatively small and fast type of military bomber aircraft that was primarily employed before the 1950s. Such aircraft would typically not carry more than one ton of ordnance.

The earliest light bombers were intended to drop their bombs in level flight over a target. During World War I some air forces began to distinguish between light bombers and the earliest purpose-built attack aircraft which carried out ground attack, close air support, anti-shipping and similar missions. After World War I, attack aircraft were typically identifiable by their ability to carry multiple fixed machine guns, automatic cannons and rockets in addition to bombs. Light bombers have often served as attack aircraft and vice versa.

The Fairchild Republic A-10 Thunderbolt II, also widely known by the nickname Warthog, is a single-seat, twin-turbofan, straight-wing, subsonic attack aircraft developed by Fairchild Republic for the United States Air Force (USAF). In service since 1977, it is named after the Republic P-47 Thunderbolt strike-fighter of World War II, but is instead commonly referred to as the "Warthog" (sometimes simply "Hog"). The A-10 was designed to provide close air support (CAS) to ground troops by attacking enemy armored vehicles, tanks, and other ground forces; it is the only production-built aircraft designed solely for CAS to have served with the U.S. Air Force. Its secondary mission is to direct other aircraft in attacks on ground targets, a role called forward air controller (FAC)-airborne; aircraft used primarily in this role are designated OA-10.

The A-10 was intended to improve on the performance and firepower of the Douglas A-1 Skyraider. The Thunderbolt II's airframe was designed around the high-power 30 mm GAU-8 Avenger rotary autocannon. The airframe was designed for durability, with measures such as 1,200 pounds (540 kg) of titanium armor to protect the cockpit and aircraft systems, enabling it to absorb damage and continue flying. Its ability to take off and land from relatively short and unpaved runways permits operation from airstrips close to the front lines, and its simple design enables maintenance with minimal facilities.

Aircraft ordnance or ordnance (in the context of military aviation) is any expendable weaponry (e.g. bombs, missiles, rockets and gun ammunition) used by military aircraft. The term is often used when describing the payload of air-to-ground weaponry that can be carried by the aircraft or the weight that has been dropped in combat. Aircraft ordnance also includes air-to-air, anti-ship and anti-submarine weapons.

Some aircraft types can carry a wide variety of ordnance – for example, the Fairchild AU-23 Peacemaker could use forward-firing gun pods, 500 and 250 pound bombs, napalm units, cluster bomb units, flares, rockets, smoke grenades and propaganda leaflet dispensers.

An attack helicopter is an armed helicopter with the primary role of an attack aircraft, with the offensive capability of engaging ground targets such as enemy infantry, military vehicles and fortifications. Due to their heavy armament they are sometimes called helicopter gunships.

Attack helicopters can use weapons including autocannons, machine guns, rockets, and anti-tank missiles such as the AGM-114 Hellfire. Some attack helicopters are also capable of carrying air-to-air missiles, though mostly for purposes of self-defense against other helicopters and low-flying light combat aircraft.

The 30 mm caliber is a range of autocannon ammunition. It includes the NATO standardized Swiss 30×173mm (STANAG 4624), the Soviet 30×155mmB, 30×165mm and 30×210mmB, the Czechoslovak 30×210mm, the Yugoslav 30×192mm, the British 30×113mmB, and the French 30×150mmB and 30×170mm cartridges.

An improvised fighting vehicle is an ad hoc combat vehicle resulting from modified or upgraded civilian or military non-combat vehicle, often constructed and employed by civilian insurgents, terrorists, rebels, mobsters, guerrillas, partisans, drug cartels, criminal organizations or other forms of non-state militias and irregular armies. Such modifications usually consist of grafting improvised armour plating and fixed crew-served weapons such as heavy machine guns or antiaircraft autocannons mounted onto the back of a utility vehicle or pickup truck.

Various militias and official militaries have improvised such vehicles ever since the introduction of the first automobiles into military service. During the 1910s and 1920s, the absence of a doctrine for the military use of automobiles or of an industry dedicated to producing them led to a great deal of improvisation in the creation of early armored cars and similar vehicles.