In December 1941, the nature of the Second World War was changed irrevocably by the German defeat at the Battle of Moscow. Up to this point Germany had been able to win each of her individual wars in a single campaign, utilising the Heer's military expertise to overcome Germany's enemies one by one and using a fixed stock of military personnel and materiel. However the Soviet Union had managed to bend before the German storm and although her pre-war army had been destroyed, had created new armies and divisions in sufficient time to halt the German advance outside the capital, so forcing the need for a second campaign. This fact changed the nature of the war from one of single military operations to one of a series of campaigns utilising national economic output to equip and sustain multiple operations continuously over a period of years. From this point onwards, the level of mobilisation of a country's economy would be a significant factor in winning or losing the war.

Which poses the question what were the relative sizes of the German and Soviet economies? After all Germany could call on the resources of an occupied Europe while the USSR had lost large amounts of territory, around 60-80 million people and 40% of its economic base. By contrast one in every three 'German' soldiers fighting on the Eastern Front was not a German national.