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| Oerlikon cannon | |
|---|---|
| Name | Oerlikon cannon |
| Type | Autocannon |
| Origin | Switzerland |
| Service | 1920s–present |
| Designer | Reinhold Becker |
| Manufacturer | Oerlikon Contraves, Rheinmetall, Hispano-Suiza |
| Weight | varies |
| Caliber | 20 mm (common) |
| Rate | varies |
| Feed | magazine, belt, drum |
Oerlikon cannon The Oerlikon cannon is a family of automatic autocannons developed from the 1920s that became prominent in World War II, Korean War, and Cold War naval and ground actions. Originating with Swiss firms and designers, the weapon series influenced autocannon design across Europe and the United States through licensing and adaptation. Renowned for compactness and reliability, the Oerlikon family saw service with navies, air forces, and ground armies including operators from United Kingdom to Japan and Brazil.
Oerlikon development began in the aftermath of World War I within Swiss industry, notably the firms in Zürich and engineers such as Reinhold Becker collaborating with companies like Maschinenfabrik Oerlikon and competing enterprises in Basel. Early designs were influenced by interwar reevaluations at the Treaty of Versailles era and contemporary work in Germany, France, and the United States. During the 1930s the design was adopted by navies preparing for contingencies that culminated in World War II, while manufacturers including Oerlikon Contraves, Hispano-Suiza, and later Rheinmetall expanded production under license to meet demand from nations such as United Kingdom, United States, Soviet Union, Japan, Italy, Netherlands, Belgium, Canada, Australia, New Zealand, India, South Africa, Brazil, Argentina, Chile, Peru, Greece, Turkey, Spain, Portugal, Sweden, Norway, Denmark, Finland, Poland, Czechoslovakia, Yugoslavia, Egypt, Iraq, Iran, Israel, Saudi Arabia, and Mexico. Postwar modernization programmes in NATO and Warsaw Pact contexts led to continued service and adaptation into systems used by Royal Navy, United States Navy, Imperial Japanese Navy, Regia Marina, Kriegsmarine, and numerous coastal and convoy protection forces.
Design evolution produced models with diverse feed systems and calibers, including 20×110mm and 20×128mm variants, as well as adaptations at 25 mm and 30 mm, and derivative systems such as the gas-operated and blowback-operated types. Notable variants emerged in licensed productions by Bofors, Mauser, SIG Sauer, Thales Group, Oto Melara, FN Herstal, General Electric, Alliant Techsystems, and Royal Ordnance. Sea mounts, twin and quad mountings, and remote-stabilized mounts were developed for platforms like HMS Belfast, USS Enterprise (CV-6), HMS Ark Royal (91), SS Normandie, HMS Prince of Wales, HMS Hood, USS Arizona (BB-39), Yamato, Musashi, Bismarck, and escort vessels engaged in Battle of the Atlantic. Airframe adaptations were trialed on types such as Supermarine Spitfire, De Havilland Mosquito, Mitsubishi A6M Zero, and Grumman F4F Wildcat in anti-ship and bomber-interception roles.
The operating principles vary between straight blowback, advanced primer ignition blowback, and short-recoil or gas-operated mechanisms depending on the variant, with designs incorporating mass, recoil spring, and delayed unlocking to manage chamber pressures derived from ammunition specifications standardized in interwar ordnance bureaus. Trained crews from organizations like Royal Artillery, United States Marine Corps, Imperial Japanese Navy Air Service, and Soviet Naval Aviation learned drills for hot-loading, clearance procedures, and emergency stoppage influenced by manuals from Admiralty, United States Navy Bureau of Ordnance, and military academies such as Staff College, Camberley and United States Naval Academy. Mount stabilisation and fire-control integration tied Oerlikon mounts to radar and director systems from manufacturers including Marconi Company, RCA, Siemens, and Thales for anti-aircraft engagement.
Ammunition types included high-explosive, high-explosive incendiary, armor-piercing, tracer, and practice rounds, many conforming to cartridge families used by ordnance bureaus in United Kingdom, United States, and Soviet Union. Ballistics and terminal effects were examined in trials at institutions such as Ballistics Research Laboratory, Royal Ordnance Factories, and Arbeitsgemeinschaft für Forschung der Wehrmacht programs, influencing munition development for anti-aircraft use against targets like Junkers Ju 87, Messerschmitt Bf 109, Ilyushin Il-2, and B-17 Flying Fortress. Specialized ammunition, including proximity-fuzed and armor-piercing capped rounds, were integrated with fire-control networks deployed on convoy escorts during engagements such as Operation Torch and the Norwegian Campaign.
Naval installations on destroyers, frigates, corvettes, aircraft carriers, and merchant vessel defenses used single, twin, and multiple mountings in point-defense roles against aircraft, torpedo boats, and missile threats, equipping fleets from Royal Australian Navy to Imperial Japanese Navy. Aircraft installations served in fixed forward-firing, dorsal, and ventral mountings in fighters, fighters-bombers, and defensive turrets on transport and bomber conversions used by units like Fleet Air Arm, United States Army Air Forces, Luftwaffe, and Soviet Naval Aviation. Coastal batteries and patrol boats under commands such as Coastal Artillery Regimentes and Coast Guards used adapted mounts in archipelagic and littoral operations in theaters including the Mediterranean Theatre, Pacific Theater of Operations, Eastern Front, and Atlantic Ocean convoy routes.
Combat evaluations in engagements such as Battle of Britain, Battle of the Coral Sea, Battle of Midway, Battle of the Atlantic, and numerous convoy actions showed strengths in close-range anti-aircraft fire and anti-motor torpedo boat defense while limitations appeared against high-altitude and heavily armored targets. After-action reports from commands including Admiral Sir John Tovey's staff, Admiral Ernest King's office, and Soviet fleet analyses highlighted rates of fire, muzzle velocity, and magazine capacity as decisive factors; these influenced retrofit programmes on ships like HMS Illustrious and USS Enterprise (CV-6). Comparative assessments with systems such as the Browning M2, Vickers S, Mauser MG 151/20, Bofors 40 mm, and later autocannon like the M61 Vulcan shaped procurement and doctrine in NATO and Warsaw Pact navies and air forces.
Widespread adoption generated a global operator list spanning Cold War and post-Cold War periods, including national services such as Royal Navy, United States Navy, Soviet Navy, People's Liberation Army Navy, Imperial Japanese Navy, Regia Marina, Marinha do Brasil, Royal Canadian Navy, Royal New Zealand Navy, Royal Australian Navy, Royal Netherlands Navy, Hellenic Navy, Turkish Naval Forces, Portuguese Navy, Chilean Navy, Argentine Navy, Egyptian Navy, Israeli Navy, Republic of Korea Navy, and Indian Navy. Modernizations led to integration in platforms alongside systems from Raytheon, Lockheed Martin, BAE Systems, and Thales Group while legacy mounts remain in service with coast guards and reserve fleets in regions from Southeast Asia to South America.
The Oerlikon family's design principles influenced later autocannon such as the M39 cannon, M61 Vulcan, ADEN cannon, DEFA cannon, and contemporary naval CIWS developments including the Phalanx CIWS and systems by Rheinmetall Defence and MBDA. Its licensing model and industrial diffusion through firms like Hispano-Suiza, FN Herstal, Bofors, and Mauser shaped 20th-century ordnance manufacturing and contributed to standards adopted by NATO and other alliances. Museums, warship restorations, and memorials at sites like Imperial War Museum, National WWII Museum (New Orleans), and preserved vessels commemorate the system's operational history while ordnance historiography in institutions such as Sandhurst and US Naval War College analyze its tactical impact.