20 mm/70 Oerlikon Mk.II (20 mm)

Description

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General info

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Available ammunition

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Comparison with analogues

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Usage in battles

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Pros and cons

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Pros:

Cons:

History

The story of the Oerlikon begins in World War I with German industrialist Reinhold Becker who developed the Becker Type 2 20 mm cannon which used an advanced primer ignition blowback action. It saw limited use during World War I, but at the end of the conflict, the Treaty of Versailles forbid further production or development in Germany resulting in the design being sold to the Swiss firm SEMAG in 1919. In 1924, SEMAG went bankrupt and the design and staff was bought out by another Swiss arms company, Oerlikon. In the build-up that preceded World War II, the British Admiralty tested the Oerlikon gun in 1934 but rejected it. In 1937, they recognized that they needed a light anti-aircraft gun for armed merchant cruisers and smaller warships. In 1938, they ordered for a new Oerlikon variant with a better rate of fire and that would be easy to service and maintain for auxiliary crews. The changes were make and resulted in the Oerlikon Mark I getting adopted by the Royal Navy with a production license. The Mark II came about in 1940 when the Fall of France led to them producing the design under license due to loss of access to Switzerland, but the location of the buffer springs was different and changes were made to make it suitable for mass production. The first ship to be commissioned with this model was the HMS Duke of York in November of 1941. About 55,000 guns were in service in the UK and Commonwealth navies by 1945. It was also used by the British on their attempt at an self-propelled anti-aircraft vehicle: the Crusader AA Mk II. However it didn't see much service due to the Luftwaffe (German Air Force) being almost non-existent by 1944.

This design also saw service in the United States Navy. The first two models were Model 1934s purchased for evaluation in 1937, but like with the Royal Navy, they were initially rejected. However, by 1940, the growing threat of the war led the Navy to reconsider and seek a one-to-one replacement for the AN-M2 Browning machine gun in the anti-aircraft. The Oerlikon thus entered widespread service by 1942 and would remain the main anti-aircraft gun of the US Navy until the introduction of the Bofors (40 mm) by late 1943. Loved by its crews for its ease of maintenance and high rate of fire, the Oerlikon Mark 2 in US service claimed 32% of all Japanese aircraft downed by the navy between the United States entry into the war in December 1941, to September of 1944. However, by September, the Japanese began engaging in kamikaze attack and the 20 mm Oerlikon was insufficient to stop these attacks leading to the Bofors being used to replace it. The Oerlikon remains in service today as a weapon for repelling boarders.

Media

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See also

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External links

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Britain and USA anti-aircraft guns
7.92 mm	BESA
12.7 mm	M2HB
20 mm	GAI C01 · M168 · Oerlikon Mk.II · Polsten
25 mm	GAU-12U
30 mm	HSS 831L
35 mm	GA-35
37 mm	M1A2
40 mm	Bofors L/60 · Dual Automatic Gun M2 · M266
	Foreign:
23 mm	ZU-23 (USSR)
35 mm	Oerlikon KDA (Swiss)