In the heat of WW2 the M4 medium series, mounting the 75mm gun, was considered to be the best tank around by the US army. When facing the new German Panther and Tiger tanks even the M4 series needed to upgrade its gun. The new 76mm M1 tank gun has far better anti-armor capabilities and is better suited to deal with the more and more heavily armored enemy tanks. The adaptation of the new gun also required a new turret when mounted on the M4A3 chassis. With its new liquid protection system to the ammunition, it was referred to as M4A3 (76)W.