The M22 Locust, officially Light Tank (Airborne), M22, was an American-designed airborne light tank which was produced during World War II. The Locust began development in 1941 after the British War Office requested that the American government design a purpose-built airborne light tank which could be transported by glider into battle to support British airborne forces. The War Office had originally selected the Light Tank Mark VII Tetrarch light tank for use by the airborne forces, but it had not been designed with that exact purpose in mind so the War Office believed that a purpose-built tank would be required to replace it. The United States Army Ordnance Department was asked to produce this replacement, which in turn selected Marmon-Herrington to design and build a prototype airborne tank in May 1941. The prototype was designated the Light Tank T9 (Airborne), and was designed so that it could be transported underneath a Douglas C-54 Skymaster transport aircraft; its dimensions also allowed it to fit inside a General Aircraft Hamilcar glider.
After a series of modifications were made to the initial prototype, production of the T9 began in April 1943. It was significantly delayed, however, when several faults were found with the tank's design. Marmon-Herrington only began to produce significant numbers of the T9 in late 1943 and early 1944, and by then the design was considered to be obsolete; only 830 were built by the time production ended in February 1945. As a result, the Ordnance Department gave the tank the specification number M22 but no combat units were equipped with it. However, the War Office believed that the tank would perform adequately despite its faults, so the tank was given the title of "Locust" and 260 were shipped to Great Britain under the Lend-Lease Act. Seventeen Locusts were received by the 6th Airborne Armoured Reconnaissance Regiment in late 1943, but mechanical problems led to the tanks being withdrawn in favor of the Tetrarchs previously used by the regiment.
In October 1944 however, the remaining Tetrarchs of the regiment were replaced by Locusts and eight were used during Operation Varsity in March 1945. The tanks did not perform well in action; several were damaged during the landing process and one was knocked out by a German self-propelled gun. Only two Locusts were able to reach their planned rendezvous point and go into action, occupying a piece of high ground along with an infantry company. The tanks were forced to withdraw from the position after several hours however, because they attracted artillery fire that caused the infantry to suffer heavy casualties. The Locust never saw active service with the British Army again and was classified as obsolete in 1946. A number of Locusts were used by foreign militaries in the post-war period; the Belgian Army used Locusts as command tanks for their M4 Sherman tank regiments, and the Egyptian Army used several company-sized units of Locusts during the 1948 Arab–Israeli War.
Development history Background The Light Tank (Airborne) M22, also known as the Locust, began development in late 1941 in response to a request by the British military earlier in the year for an airmobile light tank which could be transported onto a battlefield by glider.Flint, p. 22. At the time the request was made, the War Office considered using the equipment in Britain's fledgling airborne forces, which had been formed in June 1940 by order of the Prime Minister, Winston Churchill.Otway, p. 21. When officials at the War Office examined the equipment that would be required for a British airborne division, they decided that gliders would be an integral component of such a force. These gliders would be used to transport troops and heavy equipment, which by 1941 was to include artillery and some form of tank.Flint, p. 15. Plans to transport an airborne tank went through a number of revisions, but by May 1941 it was considered feasible for a tank weighing to be carried for in a glider, although the latter would have to be specifically designed for the task. In a conference held on 16 January 1941, it was decided that the General Aircraft Hamilcar, under development at the time, would be used to transport a single tank or two Universal Carriers.Flint, pp. 15–16.
A decision had recently been made by the War Office that light tanks were no longer to be generally used in the British Army; on the whole they had performed poorly during the Battle of France and were considered to be a liability. As a result, the Vickers-Armstrong Light Tank Mk VII Tetrarch light tank was now considered obsolete. This made it available for use by the airborne forces and it was chosen by the War Office as the tank to be transported by glider.Flint, page 16.However, it had not been designed specifically as an airborne tank or to be airmobile, and it also possessed several faults.Flint, page 11. Its size limited the possible crew to three—a driver in the hull and a gunner and commander in the turret—which was found to be too few crew members to operate the Tetrarch effectively. The gunner or commander, in addition to his own duties, had to act as loader for the 2-pounder, which caused delays in combat; a report on the tank written in January 1941 stated that since the commander had both to fight and control the tank, controlling a troop of Tetrarchs during combat would be almost impossible. The War Office was also aware that the tank had a faulty cooling system that made the Tetrarch unsuitable for service in hotter climates, such as the Middle East and North Africa.Flint, page 13.
A purpose-built airborne light tank was therefore required to replace the Tetrarch, but the decision was taken by the War Office not to produce the tank in Britain due to a lack of production capacity. Instead the American government was approached with a request that it produce a replacement for the Tetrarch.Flint, p. 23. This request was made by the British Air Commission in Washington, D.C., with a proposal calling for a tank of between and to be developed, this being the maximum weight the War Office had decided could be carried by current glider technology. The proposed tank was to have a primary armament of a main gun and secondary armament of a .30-06 Browning M1919A4, and a crew of three. The specification also called for a maximum speed of and an operational radius of . The turret and front of the hull were to have an armor thickness of between and , and the sides of the tank a thickness of . The United States Ordnance Department was given the task of developing the proposed tank, and in turn requested designs from three American companies: General Motors, J. Walter Christie and Marmon-Herrington. The design offered by Christie in mid-1941 was rejected as it failed to meet the specified size requirements, as was a modified design the company produced in November.Zaloga, M551 Sheridan, p. 5. At a conference in May 1941, the Ordnance Department chose the Marmon-Herrington design and requested that the company produce a prototype tank, which was completed in late 1941; it was designated the Light Tank T9 (Airborne) by the company and the Ordnance Department.Flint, p. 24.
Development
The T9 had a crew of three and weighed . It was armed with a main gun and a coaxial .30-06 Browning M1919A4 machine-gun, as well as two further machine-guns on the right-hand side of the bow. The main gun and coaxial machine-gun were mounted in a powered turret, which also had a gun stabilizer installed to allow the gun to be fired when the tank was moving. The T9 was powered by a 162 horse-power six-cylinder, air-cooled Lycoming engine, and the thickness of the armor varied; the front, rear and sides of the hull had a thickness of while the sloped portions of the hull had a thickness of . The tank's engine was able to give it a maximum speed of . The T9 was not primarily designed to be transported by glider, a significant change from the original request, but instead was to be carried under the belly of a Douglas C-54 Skymaster transport aircraft, using four lifting brackets welded onto each side of the hull of the tank. The turret was designed to be removable so that it could be detached and transported inside the C-54 and reattached once on the battlefield. The loading took six men about twenty-five minutes, the unloading ten minutes. On top of this the aircraft required a proper airfield on which to land.Fletcher, p. 72 However, the T9 was of the correct shape, weight and size to be carried inside a Hamilcar glider, suggesting that these dimensions had been chosen deliberately so that the tank could be transported inside a glider if required.Flint, pp. 24–25.
A number of changes were made to the prototype during testing. The main change was the addition of supporting steel beams to improve and strengthen the suspension of the tank, which increased the weight to , the maximum weight that could be carried by a Hamilcar glider.Flint, page 25. Two new prototypes were ordered by the Ordnance Department in January 1942 and were delivered by Marmon-Herrington in November 1942. They were both designated T9E1. The new tanks incorporated a number of requested changes. The turret was altered in shape; it was lightened by the removal of the power traverse mechanism and the gyro stabilizer for the main armament. The front of the hull was altered from a stepped appearance to a more sloped profile, which would provide for a better ballistic shape; the two .30-06 machine-guns were removed from the bow of the tank and the suspension was altered to try and reduce the weight of the design. However, contrary to normal practice, the Ordnance Department had placed an order for the original T9 design in April 1942, before the T9E1 models were delivered in November 1942; 500 were ordered in April and this order rapidly increased to a total of 1900, with deliveries to begin in November. However, production difficulties and design changes caused this date to be delayed several times, and it was not until April 1943 that production of the T9 actually began.