Operation Barbarossa (German: Unternehmen Barbarossa, named after Frederick I) was the code name for the European Axis invasion of the Soviet Union during World War II. It began on 22 June 1941. More than 3 million men attacked along the 2,900 km front, which made it the largest military invasion in human history. It also involved 600,000 motor vehicles and 750,000 horses.

In the Molotov-Ribbentrop pact of 1939 Germany and the Soviet Union agreed not to fight each other. Planning for the German surprise attack started in December 1940. The attack was to start on May 15, and its main objective was to destroy the Soviet military power. Some Nazi ideological goals were included, as were Soviet deposits of natural resources, which would be helpful to keep fighting the war against the Allies.

Even though the Soviets were in a terrible condition, the Axis did not complete its objectives. Tactically, the Germans held some of the most important economic areas of the Soviet Union, mainly in Ukraine. However, the Germans were pushed back from Moscow and could not do another attack as large and long as Operation Barbarossa on the Eastern Front.