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The Medium Tank M3 was an American tank used during World War II. In Britain the tank was called by two names based on the turret configuration. Tanks employing US pattern turrets were called the "Lee", named after Confederate General Robert E. Lee. Variants using British pattern turrets were known as "Grant", named after U.S. General Ulysses S. Grant. Design commenced in July 1940 and the first M3s were operational in late 1941.〔Zaloga p. 16 & 20〕 The U.S. Army needed a good tank and coupled with the United Kingdom's demand for 3,650 medium tanks immediately,〔Zaloga (Armored Thunderbolt) p. 20 & 21〕 the Lee began production by late 1940. The design was a compromise meant to produce a tank as soon as possible. The M3 had considerable firepower as it was well armed and provided good protection, but had certain serious drawbacks in its general design and shape, such as: a high silhouette, an archaic sponson mounting of the main gun, riveted construction, and poor off-road performance. Its overall performance was not satisfactory and the tank was withdrawn from front line duty — except in the remote areas of the Asian Theater where it was used by British forces as late as mid-1944 or later — as soon as the M4 Sherman became available in large numbers. In spite of this it was considered by Hans von Luck superior to the best German tank at the time of its introduction, the Panzer IV. ==History== In 1939, the U.S. Army possessed approximately 400 tanks, mostly M2 Light Tanks, with 18 of the to-be-discontinued M2 Medium Tanks as the only ones considered "modern".〔Hunnicutt p. 44〕 The U.S. funded tank development poorly during the interwar years, and had no infrastructure for production, little experience in design, and poor doctrine to guide design efforts. The M2 medium tank was typical of armored fighting vehicles (AFVs) many nations produced in 1939. When the U.S. entered the war, the M2 design was already obsolete with a 37 mm gun, 32 mm frontal armor, excessive machine gun secondary armament and a very high silhouette. The Panzer III and Panzer IV's success in the French campaign led the U.S. Army to order immediately a new medium tank armed with a 75 mm gun in a turret. This would be the M4 Sherman. Until the Sherman reached production, an interim design with a 75 mm gun was urgently needed. The M3 was the solution. The design was unusual because the main weapon — a larger caliber, low-velocity 75 mm gun — was in an offset sponson mounted in the hull with limited traverse. (The sponson mount was necessary because at the time American tank plants were incapable of casting a turret big enough to hold the 75mm main gun). A small turret with a lighter, high-velocity 37 mm gun sat on the tall hull. A small cupola on top of the turret held a machine gun. The use of two main guns was seen on the French Char B, the Soviet T-35, and the Mark I version of the British Churchill tank. In each case, two weapons were mounted to give the tanks adequate capability in firing both anti-personnel high explosive ammunition and armor-piercing ammunition for anti-tank combat. The M3 differed slightly from this pattern having a main gun which could fire an armor-piercing projectile at a velocity high enough for efficiently piercing armor, as well as deliver a high-explosive shell that was large enough to be effective. Using a hull mounted gun, the M3 design could be produced faster than a tank featuring a turreted gun. It was understood that the M3 design was flawed, but Britain〔Zaloga (Armored Thunderbolt) p. 21〕 urgently needed tanks. The M3 was tall and roomy: the power transmission ran through the crew compartment under the turret cage to the gearbox driving the front sprockets. Steering was by differential braking, with a turning circle of . The vertical volute-sprung suspension (VVSS) units possessed a return roller mounted directly atop the main housing of each of the six suspension units (three per side), designed as self-contained and readily replaced modular units bolted to the hull sides. The turret was power-traversed by an electro-hydraulic system in the form of an electric motor providing the pressure for the hydraulic motor. This fully rotated the turret in 15 seconds. Control was from a spade grip on the gun. The same motor provided pressure for the gun stabilizing system. The 75-mm was operated by a gunner and a loader. Sighting the 75-mm gun used an M1 periscope — with an integral telescope — on the top of the sponson. The periscope rotated with the gun. The sight was marked from zero to 〔later 3,500 yards〕 with vertical markings to aid deflection shooting at a moving target. The gunner laid the gun on target through geared handwheels for traverse and elevation. The 37-mm was aimed through the M2 periscope, though this was mounted in the mantlet to the side of the gun. It also sighted the coaxial machine gun. Two range scales were provided: 0- for the 37-mm and 0- for the machine gun. Though not at war, the U.S. was willing to produce, sell and ship armored vehicles to Britain. The British had requested that their Matilda and Crusader tank designs be made by American factories, but this request was refused. With much of their equipment left on the beaches near Dunkirk, the equipment needs of the British were acute. Though not entirely satisfied with the design, they ordered the M3 in large numbers. British experts had viewed the mock-up in 1940 and identified features which they considered flaws — the high profile, the hull mounted main gun, the lack of a radio in the turret (though the tank did have a radio down in the hull), the riveted armor plating (whose rivets tended to pop off inside the interior in a deadly ricochet when the tank was hit by a non-penetrating round), the smooth track design, insufficient armor plating and lack of splash-proofing of the joints.〔Fletcher ''The Great Tank Scandal'' p90〕 The British desired modifications for the tank they were purchasing, including the turret being cast rather than riveted. A bustle was to be made at the back of the turret to house the Wireless Set No. 19. The tank was to be given thicker armor plate than the original U.S. design, and the machine gun cupola was to be replaced with a simple hatch. With these modifications accepted the British ordered 1,250 M3s. The order was subsequently increased with the expectation that when the M4 Sherman was available it could replace part of the order. Contracts were arranged with three U.S. companies. The total cost of the order was approximately 240 million US dollars, the sum of all British funds in the US; it took the US Lend-Lease act to solve the financial shortfall. The prototype was completed in March 1941 and production models followed, with the first British-specification tanks produced in July. Both U.S. and British tanks had thicker armor than first planned.〔Fletcher p 93〕 The British design required one fewer crew member than the US version due to the radio in the turret. The U.S. eventually eliminated the full-time radio operator, assigning the task to the driver. After extensive losses in Africa and Greece the British realized that to meet their needs for tanks both the Lee and the Grant types would need to be accepted. The U.S. military used the "M" (Model) letter to designate nearly all of their equipment. When the British Army received their new M3 medium tanks from the US, confusion immediately set in〔Zaloga (Armored Thunderbolt) p. 18〕 between the different M3 medium tank and M3 light tank. The British Army began naming their American tanks after American military figures, although the U.S. Army never used those terms until after the war.〔Zaloga (Armored Thunderbolt) p. 19〕 M3 tanks with the cast turret and radio setup received the name "General Grant", while the original M3s were called "General Lee", or more usually just "Grant" and "Lee". The M3 brought much-needed firepower to British forces in the North African desert campaign. The chassis and running gear of the M3 design was adapted by the Canadians for their Ram tank. The hull of the M3 was also used for self-propelled artillery and recovery vehicles. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「M3 Lee」の詳細全文を読む スポンサード リンク
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