The routing of the British and French Armies in May and June 1940 by the Wehrmacht's armoured divisions caused a major rethink by the US Army's senior leadership. The result was the formation of the two armoured divisions in July 1940; the first named 'Old Ironside' and second designated 'Hell on Wheels'. In 1941, a further three armoured divisions were created; the third (Spearhead), the fourth (remained unnamed) and the fifth called 'Victory'. The following year seven more were created, the sixth, seventh, eighth, ninth, tenth, eleventh and twelfth. The final two armoured divisions formed in 1943 numbered the sixteenth and twentieth. All but one of these powerful formations went on to see service in the European Theatre of Operation (ETO); the exception being the 1st Armoured Division that served in North Africa, Sicily and Italy. These fourteen divisions proved their effectiveness against the Axis forces. In this carefully researched book military historian and much published author Michael Green explains their operational and fighting doctrine. Equipment enthusiasts will appreciate the lavish images and informed captions of the armoured fighting vehicles and other equipment employed.