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M1 240mm Howitzer

The M1 240mm Howitzer was the largest field piece used by the US Army during World War II (except for the railways guns). During World War I the US Army determined that a 240mm Howitzer was needed. Approximately 300 weapons based on a French design were built after the war. The project to replace the unsatisfactory 240mm (about 9.5") M1918 dated from the mid-1920's

In 1934 it was decided to design an all new weapon to rectify the short comings of the French weapon. The program started only in April of 1940 (prototype T1) and the M1 was standardized in May 1943, at a time when mass-production had already started [the new howitzer entered service in 1940].

On the Cassino front the Allied forces had by 22 February 1944 in addition to sixty 155-mm. Long Toms, twelve 240-mm. howitzers, which had a range slightly less than the Long Tom but a projectile more than three times as powerful. The 240-mm. howitzer and the 8-inch gun were the heaviest mobile U.S. artillery weapons. The designers had intended that both use the same mount, in line with the Ordnance Department's policy of pairing a gun (a long-barreled cannon of high muzzle velocity) with a howitzer (a short-barreled cannon of low muzzle velocity, firing shells in a relatively high trajectory) of approximately the same caliber. Next in power in the gun-howitzer pairs were the 155-mm. gun and the 8-inch howitzer, and last were the 4.5-inch gun and the 155-mm. howitzer, which were considered medium, rather than heavy, artillery.

The theater had not requested the 240- mm. howitzers. Early in October 1943 the commanding general of NATOUSA had asked the War Department for 55 tubes for 155-mm. guns, needed because the guns had been fired so much of the time at extreme ranges, necessitating the use of supercharge ammunition, that the tubes were beginning to wear out. In reply to this request, Maj. Gen. Wilhelm D. Styer, chief of staff of Army Service Forces, cabled that the tubes were not immediately available and asked whether the theater could use the 240-mm. howitzer for some missions then assigned to the 155-mm. gun.

At the time, the U.S. commanders in Italy were not eager for the 240-mm. howitzer. General Lucas, then commander of VI Corps, was "doubtful of the value of the 240 howitzer in this country." The Fifth Army Artillery officer thought that both the 240-mm. howitzer and the 8-inch gun would be "quite useful," but that "the road net and mountains make their movement and employment extremely difficult." Nevertheless, the theater agreed to accept two battalions of 240-mm. howitzers and also asked for two battalions of 8-inch howitzers, which had a range of 18,500 yards. The four battalions were to be used "for destruction of field fortifications and to relieve 155-mm. M1 units of many missions which are now causing rapid destruction [of] gun tubes."

Two battalions of 8-inch howitzers were in position on the main Italian front by 20 November 1943 and were immediately successful, especially for close support of infantry, because of their accuracy and power. The 240-mm. howitzers were delayed because the heavy tractor designed to move them was not yet available. The Ordnance Department recommended that the T2 tank recovery vehicle, with modifications, be used. In spite of the Field Artillery Board's objections, the T2 was decided upon, and the 240-mm. howitzers were shipped before the end of 1943.

Successfully moved by the T2 tank recovery vehicle, two batteries of 240-mm. howitzers were in position near Mignano on 27 January and began tiring next day. Both battalions of 8-inch howitzers were in action on the Cassino front by the end of the third week in February. Remarkably accurate, with a very small expenditure of ammunition the howitzers demolished important bridges behind the German lines, notably the bridge at Pontecorvo funneling traffic from the south and west into the Liri Valley. They were extremely effective against big buildings in Cassino and other heavy masonry structures, especially when used with the concrete-piercing fuze. According to a British artillery brigadier, the fire of the 240-mm. and 8-inch howitzer batteries was largely responsible for the ultimate reduction of the monastery at Cassino.

The heavy howitzers were ideal for the main Fifth Army front, which was "howitzer country," because they could deliver a heavy weight of explosive on the reverse slopes of mountains. In operations in the high Apennines after the capture of Rome, Maj. Gen. Alfred M. Gruenther considered the 240-mm. howitzer the most generally satisfactory artillery weapon Fifth Army had. Late in March 1944 twelve 8-inch howitzers and two 240-mm. howitzers were sent from the Cassino front to Anzio. In their first mission they demolished a tower in Littoria, a strong German observation point that the Germans had been using to direct fire on the port.

The howitzer was good, with its split trail. The carriage is the same as that used on the 8" gun M1 and requires extensive preparations to transition the gun to or from its firing position. The M35 and other tracked high-speed tractors were designed for the heavier 8" Gun M1 and its partner 240mm Howitzer M1 which was a different artillery system altogether. These were designed to be transported with gun and split-trail carriage separated and mou ted on special trailers to the gun-site where there were assembled using a crane. The transport of such a massive weapon was not easy (two separated loads) and putting it in firing position could take up to eight hours, unless special materials was available.

Its main battlefield was Italy, employed both the US and the British Army. Both continued to use them until the late fifties, when the ammunitions supplies ran out.

Caliber: 240 mm

Barrel weight: 11458.0 kg

Length: 8.40 meters

Weight of the projectile: 163.3 kg

Muzzle velocity: 701 meters per second

Range: 23 000 meters

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Page last modified: 29-05-2019 19:05:27 ZULU