The German employment of armor divisions in
the September 1939 German invasion of Poland, and especially in the May–June
1940 defeat of France, dramatically changed U.S. Army attitudes toward tanks
and their role. In April 1940 an improvised U.S. armored division, formed from
the 7th Cavalry Brigade (Mechanized) from Fort Knox, Kentucky, and the
Provisional Tank Brigade from Fort Benning, Georgia, dominated the army’s
Louisiana maneuvers. Then, in July 1940 the army created the U.S. Armored
Force, led by Brigadier General Adna Romanaza Chaffee Jr., to test the
feasibility of tank divisions. In July 1943 the Armored Force was redesignated
the Armored Command, and in February 1944 it became the Armored Center, ending
the hopes of some that the Armored Force would become a new branch of the army.
The first U.S. light tank introduced after
the start of the war in Europe was the M3 series of light tanks. Based on the
M2A3, the M3 was designed at Rock Island Arsenal in the spring of 1940 and
incorporated lessons learned in the early European fighting. Approved in July
1940, the M3 entered production in March 1941. The M3 saw extensive service in
North Africa with the British (who called it the General Stuart) and then the
Americans.
The M3 went through three different models,
eventually incorporating a gyro-stabilizer for the main gun, a diesel engine,
and an allwelded turret and hull (the first being riveted). It also received
two jettisonable 25-gallon fuel tanks to increase its range in the desert. The
problem with its riveted armor was that even a glancing shot to the hull by an
enemy shell could sheer the heads off rivets and send the remainder flying
around the inside of the tank, causing serious personnel injuries and/or
igniting ammunition or damaging the engine.
The M3 weighed some 27,400 pounds, had a
crew of four, maximum 51mm armor, and was armed with a 37mm gun in the turret
and 3 x .30-caliber machine guns. The M3A1 version of 1942 eliminated the
turret cupola to reduce overall height and also did away with the two sponsoned
machine guns, fired remotely by the driver. These had proved of limited use,
and doing away with them reduced the tank’s weight and increased its internal
storage.
The final version M3A3 entered production
in early 1943. Weighing some 31,800 pounds, it had a new all-welded hull that
was enlarged by extending the sponsons and increasing the driver’s compartment
forward and upward. This extra room allowed for additional ammunition storage
and fuel tanks.
Although the M3 in its various models
performed well in its primary reconnaissance role, the tank was both
undergunned and underpowered. The M3 proved a welcome addition to British armor
assets in North Africa in 1941–1942, and its crews there thought highly enough
of the reliable M3 to refer to it as “Honey.” The U.S. Army declared the M3
obsolete in July 1943; it remained in the service of other nations through the
end of the war and beyond.
The follow-on to the M3 was the M5 series,
also designated the General Stuart. The same basic design as the M3, it had
twin Cadillac automobile engines as well as the commercial Cadillac hydromatic
transmission used in automobiles. Officials of the Cadillac Division of General
Motors Corporation suggested this change to the Ordnance Department, which
converted a standard M3 in the fall of 1941. Subsequent tests proved
satisfactory.
Originally to be the Light Tank M4, the new
tank was designated the M5 to avoid confusion with the M4 medium Sherman tank
then entering production. Recognizable by its stepped-up rear deck to accommodate
its new power plant, the M5 had the same hull as its predecessor, save for a
sloping glacis. The M5 had a crew of four, weighed some 33,000 pounds with
maximum 67mm armor, and had armament of one 37mm gun and two .30-caliber
machine guns.
Superior to the M3, the M5 was not produced
in large numbers because of the appearance of its successor, the heavier M24.
The U.S. Army declared the M5 to be “substitute standard” in July 1944. In
British service both the M5 and M5A1 were known as the Stuart VI.
In May 1941, following consultation with
the Armored Force and the Army Air Corps, the Ordnance Department called for
the manufacture of an airborne tank of 8 tons, about half the weight of an M5,
with carriage dimensions so that it would be transportable either inside or
under the belly of a cargo aircraft. Christie, General Motors, and
Marmon-Herrington all submitted designs. The Marmon-Herrington design was
judged to be best, and the government ordered a test model, designated the T9.
Following initial testing, Marmon-Herrington built two other pilot models.
The production model, the M22 Locust, had a
rolled plate hull and a cast turret. Four hull brackets facilitated slinging
the hull under an aircraft. It also featured an easily removable turret to facilitate
air transport. The Locust could also be transported in the hold of a British
Hamilcar glider. The M22 was of conventional, although compact, design, but its
thin armor gave it limited tactical application. It had a battle weight of
16,400 pounds, a crew of three, a 162- hp engine, a maximum speed of 40 mph,
maximum 25mm armor, and mounted a 37mm main gun and one .30-caliber machine
gun.
The M22 was a specialized, limited
production tank. The follow on U.S. tank to the M5 was the M24 Chaffee. Based
in large part on observations of British experience in the Western Desert with
the M3 series of light tanks, the U.S. Army determined that its light tanks
should mount a 75mm gun. The M5 series could carry the larger 75mm, but only
with sharply restricted interior storage space; this forced the design of a new
tank.
In April 1943 the U.S. Army Ordnance
Department and Cadillac, which had produced the successful M5, began work on a
new design that was to make use of the best aspects of the M5, such as the twin
Cadillac engines and hydromatic transmission, while incorporating changes based
on combat experience. The new design incorporated angled hull surfaces for
maximum crew protection, and road wheels on torsion arms provided a smoother
ride.
The first of two pilot models, delivered in
October 1943, proved so successful that the Ordnance Department immediately
ordered production, first for 1,000 vehicles, and then 5,000. At first
designated the T24, the new tank was delivered to U.S. units late in 1944,
replacing the M5. It was designated the M24 in May 1944.
The all-welded, 40,500-pound M24 had a crew
of five, two 110- hp engines that delivered a maximum speed of 35 mph, maximum
25mm armor protection, and mounted a 75mm gun and three machine guns: two
.30-caliber (one coaxial with the main gun) and one .50-caliber for
antiaircraft protection. This highly successful tank combined a rugged design
with high speed, simplicity, reliability, and heavy armament for its size. The
M24 was also employed by the British Army, and it continued in U.S. service
well after the war. It appeared in a variety of guises, all of which had the
same engine, power train, and suspension system. These included howitzer and
mortar motor carriages. The M24 could also be easily fitted with a dozer blade
when necessary.
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