The U.S. Navy used Bofors 40mm multi-barrel anti-aircraft systems during and after World War II. They were among the most effective and widespread anti-aircraft defense systems on ships at the time.

Bofors 40mm guns were typically mounted in twin or quad mounts, with the quad mount version being particularly prized for its high firepower. Each barrel was 40mm in caliber and capable of firing large numbers of anti-aircraft shells in rapid succession, crucial for defending ships against air attacks.

This system was characterized by a high rate of fire, and its effectiveness was increased by the use of ammunition with time fuses that exploded near the target, increasing the chance of damaging or destroying the attacking aircraft.

Bofors systems were widely used on a wide range of ships, from destroyers to aircraft carriers, and played a crucial role in defending Allied fleets from air attacks, particularly in the Pacific. Although they were eventually superseded by more modern missile and artillery systems, their influence on the development of anti-aircraft defense systems was significant.