World War II, the Allies had begun considering replacements for the 20mm Oerlikon cannon, which had been widely used during the war, particularly for anti-aircraft and close defense purposes on ships. While the Oerlikon cannon had proven effective in many situations, particularly against smaller aircraft and for close-in defense, there were several factors that led to the search for a more capable replacement.
Limitations of the Oerlikon 20mm Cannon
The Oerlikon 20mm cannon, though widely used and produced in large numbers by the Allies, had certain limitations:
Limited Firepower: While the Oerlikon was effective against smaller aircraft, it lacked the firepower to engage larger enemy bombers or to provide substantial protection against swarming waves of aircraft.
Range and Accuracy: The relatively short range and limited accuracy of the 20mm cannon meant that it could be less effective against fast-moving and higher-altitude threats, especially in the latter years of the war when enemy aircraft became faster and more maneuverable.
Ammunition Performance: The relatively small caliber of the Oerlikon meant that it did not have the same explosive impact as larger-caliber anti-aircraft weapons. Against heavily armored aircraft, its shells were less effective compared to larger caliber weapons.
Allied Considerations for a Replacement
As the war progressed and new technologies emerged, the Allies began to seek more powerful and capable anti-aircraft systems to replace or supplement the Oerlikon. Some of the primary options considered included:
Bofors 40mm Gun: The Swedish-made Bofors 40mm gun was a popular and effective alternative to the Oerlikon. It had a larger caliber, more powerful ammunition, and a better rate of fire. The Bofors was much more effective against medium to large aircraft, and it became one of the most widely used anti-aircraft guns by the Allies, often seen on naval ships and in coastal defense positions.
Heavy Machine Guns and Auto-Cannon Systems: Some early replacements were considered to be larger caliber machine guns or automated systems capable of providing higher rates of fire and more powerful rounds. These systems were generally effective at close range, but they lacked the reach of larger-caliber artillery and needed to be complemented by other anti-aircraft systems for a more comprehensive defense.
The 40mm and 3-inch Anti-Aircraft Guns: In addition to the 40mm Bofors, the U.S. developed and used the 3-inch/50 caliber anti-aircraft gun, which was more effective at higher altitudes. These weapons were often mounted on ships and shore installations to provide better defense against both high-flying bombers and low-altitude attackers.
Radar-Guided Systems and Larger-caliber Automatic Weapons: By the end of the war, radar-guided anti-aircraft systems and larger-caliber automatic weapons began to emerge as potential replacements. These systems, such as the U.S. Navy’s 5-inch/38 caliber gun, were designed to offer both range and effectiveness, allowing for more precise targeting of enemy aircraft at greater distances.
Post-War Developments
After the war, the need for a replacement for the Oerlikon became more urgent as threats from jet aircraft and missiles emerged. The post-war era saw the development of more advanced, rapid-fire automatic weapons and radar-guided systems, which gradually phased out older designs like the Oerlikon. Some of the new anti-aircraft systems, such as the Phalanx CIWS (Close-In Weapon System), were designed specifically to handle the new generation of supersonic threats that were far more challenging than the aircraft of World War II.