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M1 was designed to replace the World War I era 240 mm howitzer M1918, which was based on a 1911 French design and was outdated by World War II.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 high explosive projectile . 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 Germany's Siegfried Line.
The 240 mm howitzer M1 was designed together with the longer-ranged 8-inch gun M1, and they 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 recapture of Manila in 1945, but few targets there were fortified heavily 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 Taiwan, stationed in hardened bunkers of the frontline Kinmen and Matsu Islands.
Development
During World War I, the United States Army received several British 9.2-inch (233.7 mm) howitzers, but was more impressed by the French Mortier de 280 modèle 1914 Schneider. 330 of the latter weapon, in a slightly modified form, were built under license by the mid-1920s as the M1918 240 mm howitzer. In 1925, it was concluded that the design was flawed, so it was decided to build a new weapon; design work, however, did not begin until 1934 and resulted in the modification of existing weapons as the M1918A1M1, but the project stalled because of limited funding. In April 1940, another design program was begun, and resulted in the 240 mm Howitzer T1. Production began in November 1942, and the piece was standardized in May 1943 as the 240 mm Howitzer M1 on Carriage M1.
Service
Transport
A pair of three-axle, six-wheeled transport wagons were developed – one for the cannon tube, and one for the carriage. These transport wagons were also used with the 8-inch gun. These were standardized as the M2 and M3. The M2 wagon carried the carriage and the M3 wagon carried the barrel and recoil system. This separate configuration required the use of the 20-ton M2 truck-mounted crane for setup. The crane also included a clam-shell bucket that was transported on a trailer and used to dig the recoil pit for the gun. It took about two hours to emplace the gun.
The transport wagons were initially intended to be towed by the Mack NO -ton heavy truck. Because the truck was a wheeled vehicle, it had problems in soft ground such as mud due to its high ground pressure. The M6 High Speed Tractor, a tracked vehicle which was explicitly designed for towing the 8-inch gun and 240 mm howitzer was standardized in June 1943 but would not enter production until February 1944, so the Ordnance Department improvised in the meantime. Surplus M3 Lee-based M31 and M32B1 tank recovery vehicles and M10A1 tank destroyers were quickly modified and tested. These proved to be satisfactory and were adopted for use as the M33, M34, and M35 Prime Movers, respectively. Likewise, the wheeled transport wagons loaded with the heavy gun components often became bogged down in soft ground, so the Ordnance Department developed the T17E1 carriage transport wagon with a pair of tracked bogies, and the T16E1 gun transport wagon with three medium tank bogies on each side. One 240 mm howitzer battalion was deployed to the Pacific in 1945 equipped with these carriages.