Operation Barbarossa (Unternehmen Barbarossa) was the German codename for Nazi Germanys invasion of the Soviet Union during World War II. It was to be the turning point of the Nazis fortunes, and would arguably result in the capitulation of Germany. The Eastern Front that was opened with Operation Barbarossa would become the biggest theatre of war in World War II, with some of the largest and most brutal battles, terrible loss of life, and miserable conditions for Russians and Germans alike.
Before Operation Barbarossa, the Germans and the Russians were ostensibly on friendly terms, having signed the unexpected Molotov-Ribbentrop Pact shortly before the German and Soviet invasion of Poland. It was a non-aggression pact in which the Germans and the Russians had agreed how to divide up Eastern Europe between themselves. The pact was unexpected because of their mutual hostility before that time. But Hitler had long wanted to conquer Russia itself in order to enslave its untermensch Slavic population. So the pact was simply for short-term convenience and the Nazis had no qualms about breaking it to pursue their interests.
Operation Barbarossa was largely the brainchild of Hitler himself. His general staff advised against fighting a war on two fronts. But Hitler considered himself a political and military genius, and indeed at this point in the war he had achieved a whole series of lightning victories against what appeared to be insurmountable odds. First, his brashness and willingness to take risks, combined with the discipline of his troops and the Blitzkrieg tactics, had won him the Sudetenland and Czechoslovakia with hardly a struggle, then Poland, Denmark and Norway with only slightly more trouble. Then he achieved the rapid collapse of the French armies by running through Belgium and around the Maginot Line. Britain appeared to be holding out through sheer will. Hitler thought it was time to turn on his former friend in the East, arguing that for the Wehrmacht it was important to strike before the Red Army commenced the foreseen invasion of Germany.
Hitler was overconfident after rapid success in Western Europe, expecting victory in a few months and not preparing for a war lasting into the winter. He did not even equip his troops with cold weather gear. He hoped a quick victory against the Red Army would encourage Britain to accept peace terms.
In preparation for the attack, Hitler moved 2.5 million men to the Soviet border, launched many aerial surveillance missions over Soviet territory, and stockpiled vast amounts of materiel in the East. Yet the Soviets were still taken completely by surprise. This has mostly to do with Stalin's unshakeable belief that the Germans would not attack only two years after signing the Molotov-Ribbentrop Pact. He also was sure the Nazis would finish their war with Britain before starting a new one. Despite repeated warnings from his intelligence system, Stalin refused to give them credence, believing the information to be British plants designed to spark a war between the Nazis and the USSR. The Germans also aided in this deception. They told Stalin that the troops were being moved to bring them out of range of British bombers. They also explained that they were trying to trick the British into thinking the Nazis were planning to attack the Soviet Union, while in fact the troops and supplies were being saved up for an invasion of Britain. It has been established that communist spy Dr. Richard Sorge gave Stalin the exact launch date; also Swedish cryptanalysts lead by Beurling knew the date beforehand.
Readers of Hitler's Mein Kampf ("My Struggle") should not have been surprised to see him invade the Soviet Union. In that book, he makes clear his belief that the German people needed land (Lebensraum - "living space"), and that it was to be looked for in the East. However, Stalin was convinced Hitler would not yet attack.
On June 22, 1941, Operation Barbarossa took off eventually. It encompassed a total troop strength of 3 million men, making it the biggest single land operation ever. While being initially successful - almost reaching Moscow by early December - it is often proposed that the fatal design flaw of the operation was the postponement from May 15th because Hitler wanted to intervene against an anti-German overthrow in Yugoslavia. This cut off 5 weeks off the already short Russian summer to spend midfield. However, during the campaign, Hitler ordered the main thrust that had been heading toward Moscow to be diverted southward in order to help the southern army group capture Ukraine. This move delayed the assault on the Soviet capital, although it also helped to secure the central army group's southern flank. By the time they turned their sights on Moscow, the mud after the autumn rains and eventually the winter snowfall ground their advance to a halt. Thus they were prevented from much further gain, although this was also in part to stronger resistance from the Russians than had been expected. German logistics also became a major problem as a result of the great length of their supply lines.
It was the stated policy of the Nazis to kill, deport, or enslave the Russian population, whom they considered inferior, and to use the land for Lebensraum.
The turning point of the operation was when Nazi troops advanced within sight of the spires of the Kremlin. It was as close as they would ever get, for Stalin's troops defended Moscow ferociously, and drove the Germans back into the frozen wastes of Russia as the winter advanced.