The 240 mm howitzer M1, popularly nicknamed the "Black Dragon", was a towed howitzer used by the United States Army. The 240 mm M1 was designed to replace the World War I era 240 mm Howitzer M1918 which was based on a 1911 French design and was outdated by World War II. The project to replace the M1918 began in 1941. The 240 mm howitzer was the most powerful weapon deployed by US field artillery units during World War II, able to fire a 360 lb (160 kg) high explosive projectile 25,225 yards (23 km). It was the largest field piece used by the US Army during the war except for naval ordnance adapted into railway guns. The weapon addressed the requirement for super heavy field artillery capable of attacking heavily reinforced targets like those likely to be found along the Siegfried Line. It
The 240 mm howitzer M1 was designed together with the longer ranged 8-inch Gun M1, and they both shared a related carriage. While use of the 8-inch gun was limited due to excessive bore wear and poor accuracy, the howitzer saw considerable action during World War II in Europe due to its effectiveness against difficult targets such as heavy concrete fortifications. It was also used in the Pacific campaign, notably in the Battle of Manila, but few targets there were heavily-fortified enough to justify its use.
The US army retained the 240 mm howitzer after World War II, and later deployed it in the Korean War. The howitzer remained in US service until ammunition stocks were exhausted in the late 1950s.
The 240 mm howitzer M1 is still in service with the Taiwan's Republic of China Army, stationed in hardened bunkers of the frontline Kinmen and Matsu Islands.