The Bofors 40mm gun was the most popular medium-weight anti-aircraft gun used by most of the western Allies, as well as other forces, during the Second World War. It is often referred to simply as the Bofors Gun.
Development of the 40mm gun can be traced back to a Swedish Navy requirement in 1929 for a more capable anti-aircraft gun to replace their 2 pounder ‘Pom-Poms’ guns ordered from Vickers in 1922. Bofors began designing a prototype gun which they based on one of their previous designs, the 57mm semi-automatic gun, which had been developed as an anti-torpedo boat weapon during the late 1890s. During this period, Krupp had purchased a third share in Bofors, and had begun to update the Bofors factories with modern equipment and metallurgy, but the new 40mm gun design was kept secret from them. Testing of the prototype began in 1927, and a major problem with loading of the gun was discovered, various fixes were tried, and eventually a solution was found.
By 1930 testing of the prototype had been completed, but more work was required to make the weapon suitable for production. This work was completed in October 1933. Until now, all work on the gun had been focussed on naval applications for the gun, but in 1935 Bofors, began development of a suitable towable carriage for a land based version. First ordered by Belgium in August 1935, further orders were soon forthcoming, including those from the United Kingdom and the United States of America.
By the end of the Second World War, aircraft speeds had increased so much that the Bofors gun couldn’t get enough rounds in the air to counter the air threat. Bofors returned to their drawing boards and designed an improved version which featured a slightly larger round and an increased rate of fire. Production began in 1947 and first entered Swedish service in 1951. Foreign sales began and in November 1953, and it was soon accepted as the NATO standard anti-aircraft gun, and was being produced in its thousands.
The Bofors gun remained in front-line service well into the 1980s with the British Armed Forces, and is still in operation with a number of export customers around the world today.
