Operation Barbarossa was the code name for the Axis invasion of the Soviet Union, starting Sunday, 22 June 1941, during World War II. The operation stemmed from Nazi Germany's ideological aims to conquer the western Soviet Union so that it could be repopulated by Germans, to use Slavs as a slave-labor force for the Axis war-effort, and to seize the oil reserves of the Caucasus and the agricultural resources of Soviet territories. Stalin's reputation as a brutal dictator contributed both to the Nazis' justification of their assault and their faith in success; many competent and experienced military officers were killed in the Great Purge of the 1930s, leaving the Red Army with a relatively inexperienced leadership compared to that of their German counterparts. In the middle of 1940, following the rising tension between the Soviet Union and Germany over territories in the Balkans, an eventual invasion of the Soviet Union seemed to Hitler to be the only solution. While no concrete plans were made yet, Hitler told one of his generals in June that the victories in Western Europe finally freed his hands for his important real task: the showdown with Bolshevism.