[2] 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 (23,066 m).
[4] 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.
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.
[9] The first operational use of the super-heavy 240 mm howitzer was by the 697th and 698th Field Artillery Battalions of the U.S. 5th Army at the Anzio Beachhead in Italy in January 1944.
[5] Their fire was accurate enough not only to knock enemy artillery out of action, but also to destroy targets as small as German heavy tanks.
[5] US super-heavy artillery also played a role in countering the infamous Anzio Annie railway gun and putting it out of action.
[11] Army ordnance officers credited the "devastating fire power and incredible accuracy" of the 240 mm howitzer in playing a decisive role in the Italian Campaign.
During the Korean War, twelve 240 mm howitzers were brought out of "mothballs" and sent to the front lines to deal with deep bunkers and fortifications built by the Chinese that could not be effectively attacked by the smaller artillery weapons then on hand.
On that day, the first round was fired by Baker battery of the 213th at a target on top of a hill called "the donut" by aerial observers.
The guns were put on rails to enable the howitzers to deploy outside for fire missions and to retreat inside their hardened bunkers/tunnels for protection (capable of withstanding direct hits from aerial bombs) when needed.
[13][14] The 240 mm howitzer M1 was broken down into two loads for travel (the barrel and recoil mechanism and the carriage), each towed on a six-wheeled wagon by a Mack NO 7½-ton 6x6 truck or another heavy prime mover such as the M33 or M35.