How One Swedish Gun Ruined More Enemy Planes Than Any Other in WWII

A Neutral Nation’s Surprising Weapon

Neutral Sweden is rarely remembered as a major arms supplier in the Second World War, but one of its inventions became the most effective anti-aircraft weapon of the conflict. The Bofors 40mm gun, designed in the late 1920s, went on to shoot down more aircraft than any other system. It protected Allied ships and airfields while also guarding German positions, proving that Swedish neutrality did not prevent Swedish arms from shaping the war.

The story began in 1928, when Swedish Navy Captain Victor Hammer watched his fleet’s anti-aircraft drills fail. The existing weapons could not hit fast-moving aircraft. He turned to the Bofors company, a steel manufacturer with experience in heavy industry, and demanded a gun that could finally meet the challenge of modern aviation. What emerged would later destroy over 20,000 aircraft worldwide.

The Gun’s Unique Features

The Bofors 40mm was built with precision engineering. It fired two-pound explosive shells at a rate of 120 rounds per minute, far faster than similar weapons of its day. Its automatic ammunition feed allowed continuous fire, while hydraulic controls gave a single operator the ability to track aircraft with fingertip movements. Another breakthrough was the predictor sight, which calculated where a plane would be instead of aiming at where it was. This greatly improved accuracy against fast, diving aircraft.

Crews soon trusted the weapon. A gunner from the USS Enterprise later recalled switching from older three-inch guns to the Bofors. At Pearl Harbor, the older guns took half a minute to reload, but the Swedish-designed weapon never stopped firing. In his words, it saved his life during kamikaze attacks.

Spread Across the World

Sweden’s neutrality created unusual situations. The government allowed Bofors to sell licenses widely, and soon Britain, Belgium, Norway, Poland, and the United States were building the weapon. Hungary and Finland, aligned with Germany, also used it. Japan produced copies after capturing examples. Even Germany relied on Norwegian-built Bofors guns to defend Berlin. By 1943, factories in America alone had produced 60,000 of them, while Britain added 19,000 more. The Soviet Union and Japan copied thousands without licenses.

Because it was so widespread, the Bofors often faced itself in combat. Swedish technicians even received reports from both sides, which helped them refine the design. The gun’s presence in nearly every theater meant that both Allied and German pilots had to adapt their tactics.

Deadly Results in Combat

The Bofors proved decisive in major operations. During the Normandy invasion in 1944, ships armed with the gun formed a protective barrier over the beaches. Out of 435 German aircraft sighted on D-Day, 312 were destroyed by Bofors fire. In the Pacific, young sailors used single mounts to bring down waves of kamikazes. At Okinawa, a 19-year-old seaman destroyed five attacking planes in just four minutes with one mount.

Later improvements made it even deadlier. The introduction of proximity fuses in 1944 allowed shells to explode near targets without direct hits, increasing effectiveness fourfold. Japanese pilots nicknamed them “black dragons” because of the dark bursts that marked fatal encounters.

Legacy of the Bofors

By the war’s end, the gun had downed more enemy aircraft than all fighters and heavy flak guns combined. The irony was that Swedish neutrality meant Bofors guns also destroyed Allied planes. After 1945, surplus examples spread to 90 nations, and upgraded versions still defend warships today. Designed to be accurate, simple to build, and reliable in any climate, the Bofors 40mm became history’s most successful anti-aircraft gun—an invention from a neutral country that armed both sides in humanity’s deadliest conflict.