On this day in 1941, Operation Barbarossa began. It was the largest German military operation of World War II. Despite promises made in 1939 with the Molotov-Ribbentrop pact, an agreement between Nazi Germany and the Soviet Union that divided Eastern Europe between themselves, Hitler always regarded the Soviet Union as a key location for German Lebensraum, or expansion. The non-aggression pact was a tactical maneuver to hold off the war on the Eastern Front while Hitler focused on the ‘Low Countries’: Belgium, the Netherlands, and Luxembourg. On December 18, 1940, Hitler signed the first operational orders for the invasion of the Soviet Union to take place the next year. The Germans planned for war with the Soviet Union to annihilate Judeo-Bolshevism, which they believed lived on in the Communist government and citizens alike; their intention was to create mass casualty. Just before the invasion, the German High Command agreed with the SS to have mobile killing squads — known as the Einsatzgruppen — march in the army’s rear. The Germans initiated “The Hunger Plan” in 1940 to starve out the Soviets, as the Wehrmacht (Nazi armed forces) looted for supplies along the way rather than being supplied by Berlin. On June 22, 1941, three German army groups, totaling more than three million men, attacked the Soviet Union across a broad front. They were supported by 650,000 additional troops from Romania and Finland. As the War went on, troops from Italy, Croatia, Slovakia, and Hungary joined the fighting. The front stretched from the Baltic Sea in the north to the Black Sea in the south. As the Germans advanced into the Soviet Union, they were followed by the Einsatzgruppen and other SS and police units, who were given the following tasks: Identifying and eliminating people who might organize and carry out resistance to the German occupation forces; identifying and concentrating groups of people who were considered potential threats to German rule in the East; establishing intelligence networks, and securing key documentation and facilities.These directives were to be carried out by any means necessary, and quickly made the Eastern Front the bloodiest stage of the war. The Einsatzgruppen commonly initiated shooting operations, targeting primarily Jewish men and Communist Party officials. They also assisted the German army in establishing ghettos for Soviet Jews. Other crimes included liquidating remaining psychiatric hospitals by killing patients and taking over the facility as their own, killing civilians and looting their homes for food and supplies, and not allowing safe surrender for Red Army troops. After months of fighting, the German troops became exhausted as resistance by Soviet soldiers and citizens alike only grew. On December 6, 1941, the Soviets launched a massive counter-attack that pushed the German troops back to Moscow. This left the Germans in disarray and led to a victory for the Soviets at the Battle of Stalingrad in February 1943, which many historians regard as the breaking point of the German army in WWII. However, the fighting did not end until the Soviets secured a victory at the Battle of Berlin on May 2, 1945.