On 1 September 1939, when Germany attacked Poland, the Wehrmacht numbered 3,180,000 men. It eventually expanded to 9,500,000, and on 8-9 May 1945, the date of its unconditional surrender on the Western and Eastern Fronts, it still numbered 7,800,000. The Blitzkrieg period, from 1 September 1939 to 25 June 1940, was 10 months of almost total triumph for the Wehrmacht, as it defeated every country, except Great Britain, that took the field against it. In this first of five volumes examining the German Army of World War II (1939-1945), Nigel Thomas examines the uniforms and insignia of Hitler's Blitzkrieg forces, including an overview of the Blitzkrieg campaign itself.