The M4 Sherman, officially Medium Tank, M4, was the most numerous battle tank used by the United States and some of the other Western Allies in World War II. In spite of being surpassed by German medium and heavy tanks late in the war, the M4 Sherman proved to be very reliable, cheaper to produce and available in greater numbers. Thousands were distributed through the Lend-Lease program to the British Commonwealth and Soviet Union. The tank was named by the British for the American Civil War General William Tecumseh Sherman.

The M4 Sherman evolved from the interim M3 Medium Tank,^{[N 1]} which had its main armament in a side sponson
mount. The M4 retained much of the previous mechanical design but put
the main 75 mm gun in a fully traversing turret. One feature, a one-axis
gyrostabilizer,
was not precise enough to allow firing when moving but did help keep
the reticle on target, so that when the tank did stop to fire, the gun
would be aimed in roughly the right direction.^[6]
The designers stressed mechanical reliability, ease of production and
maintenance, durability, standardization of parts and ammunition in a
limited number of variants, and moderate size and weight. These factors,
combined with M4 Sherman's then-superior armor and armament, outclassed
German light and medium tanks of 1939–42. The M4 went on to be produced in large numbers. It spearheaded many offensives by the Western Allies after 1942.

When the M4 tank went into combat in North Africa
with the British Army at El Alamein in the autumn of 1942, it increased
the advantage of Allied armour over German armor and was superior to
the lighter German long-barrel 50 mm-gunned Panzer III and the short-barrel 75 mm-gunned Panzer IV then in service.^[7]
For this reason, the US Army believed the M4 would be adequate to win
the war, and no pressure was exerted for further tank development.
Logistical and transport restrictions, such as limitations imposed by
roads, ports, and bridges, also complicated the introduction of a more
capable but heavier tank. Tank destroyer battalions
using vehicles built on the M4 hull and chassis, but with open-topped
turrets and more potent high-velocity guns, also entered widespread use
in the American army. Even by 1944, most M4 Shermans kept their dual
purpose 75 mm M3.^[9]
By 1944 and 1945, the M4 was inferior to German heavy tanks but was
able to fight on with mutual support from numerical superiority and with
support from growing numbers of fighter-bombers and artillery pieces.^[10]