The tank which was to become famous as the Sherman was a result of the urgency of the US military after observing the early campaigns of WW2 in Europe.
At the outset, the USA had little more than light tanks, admittedly with proven components but lacking heavy armament. The decision to go for a 75mm gun prompted almost parallel developments: the M3 (known as the Grant or Lee) and the M4 Sherman.
The former was really a stopgap, created by simply fitting the 75mm gun in the hull as opposed to the turret. This allowed a heavier tank to be produced more quickly. The M3 prototype was delivered in January 1941 and production started in July 1941. Just prior to that, in April, the design for the M4 was selected; essentially a modified M3 hull and chassis topped with a new turret housing the 75mm gun from the M3 hull. The prototype was completed in September 1941 and production began in October. The new tank rapidly proved itself durable and reliable; something British crews (the earliest users) found as a welcome change after the unreliability and fragility of their own earlier tanks.
Initially used in North Africa, the Sherman proved itself a measure for the Panzer IIIs and IVs there, but by early 1943, with the arrival of the Tiger I, the limitations of its armament and armour were becoming apparent. Nevertheless, the sheer numbers rolling off the production lines meant that Allied losses could easily be made good, whereas Axis losses never could. This was the secret of the Sherman’s success: reliability and numbers.
Battlefield experience was not ignored, however. Additional armour was added in crucial places or for specific roles. ‘Wet’ ammunition storage was introduced to cut down on the risk of fires and track and suspension modifications helped with performance over rough ground. But it was the main gun which needed to be addressed: except at virtually point blank range and from certain angles, the 75mm could not overcome the Panther and Tiger. The British solution to this was the ‘Firefly’ – a Sherman with the 17 pounder anti tank gun in a modified turret. The American solution was to fit a new turret from the experimental T20 tank, mounting a 76mm gun. This version featured more and more from its introduction in mid 1944 to the end.
But it was the numbers which made the difference. Nearly 50,000 Shermans were produced between 1942 and the end of the war, and were used in all theatres of operations. Its engineering fundamentals were so reliable and strong that the chassis was used in a variety of other vehicles – self-propelled artillery, tank destroyers, and combat engineer vehicles. It soldiered on beyond 1945, in Korea, French Indo China, the Middle East, with the final variants still operational into the 1960’s.