Operation Barbarossa
Operation Barbarossa was the 1941 German invasion of Russia. It was launched on June 22, 1941, with three Army Groups, which swept across the Russian plains eastwards towards their objectives. It was the largest military campaign of World War II. The German invasion of Russia began at 05:10 hours, when mechanized infantry and armored divisions of the Wehrmacht's Army Group Center crossed the Bug River into Soviet-occupied Polish territory. The military plan to invade Russia had carefully been designed by field marshal Franz Halder and Hitler himself in December 1940 and it would be executed in the same manner as Fall Weiss and Fall Gelb, which means through a Blitzkrieg surprise attack.
Reasons for attacking Russia
The rationale to invade the Soviet Union was three-fold: 1) ideological: it was necessary to oust Stalin and the communist regime from power to eliminate a dormant threat of a communist expansion towards Western Europe in the form of political influence (indoctrination of young people at university centers) or militarily; 2) geopolitical: by expanding towards the east, Hitler would ensure that the whole of Eastern Europe and Asia would be under Nazi Germany's sphere of influence; 3) economically: Adolf Hitler would have a large and permanent flow of raw material and natural resources for a growing mighty Germany, enabling the Third Reich even to export commodities and manufactured products. This territorial expansion of Germany was called Lebensraum (living space in German).
Hitler had always wanted to expand eastwards, not westwards, for it had never been his intention to engage Great Britain or the United States of America in a war. He had invaded and conquered France the year before only to secure Germany's back, avoiding a two-front armed conflict, and, at the same time, recover Alsace and Loraine, which had been wrenched away from Germany at the end of the Thirty Year War and then again at the end of World War I, with the Treaty of Versailles.
German Soldier in a Russian village during Operation Barbarossa.
Below, map showing the directions of the German attacks in the Russian Campaign according to the Operation Barbarossa's plan designed on December 18, 1940.
Below, positions the opposing forces occupied right before the offensive was set in motion on June 22, 1941.