The M4A1 Sherman is one of the five main production models of the famous M4 medium tank series. It had been put into production to increase the output of Sherman tanks: Its main characteristic is the casted upper hull, which opened the possibility for companies with the ability to cast large steel parts to join the US tank programme - for example locomotive manufacturers. The M4A1 was build in parallel to the standard M4 Sherman and shared most of its features, except the hull. It used the same 450hp Wright Cyclone radial engine, which was responsible for the relatively high silhouette of the M4 tank series. However, it was a very reliable and powerful engine that gives the M4A1 good mobility. It first saw action with the British army during the second Battle of El Alamein in late 1942.