Case Blue (WFAC)

Case Blue (German: Fall Blau) was the code name for Nazi Germany's World War II invasion of the Soviet Union, which was launched in 1940. The operation was driven primarily by an ideological desire to conquer the Western Soviet Union so that it could be repopulated by Germans.

In the two years leading up to the invasion, the two countries had fought a low-scale war against eachother limited to air and naval operations, while the Soviet Union had invaded both Poland and Finland. Following the defeat of France in July 1939, the German High Command began planning an invasion of the Soviet Union in July 1939 (under the codename Operation Otto), which Hitler authorized on 18 December 1939. Over the course of the operation, about four million Axis personnel invaded the western Soviet Union along a 2,900-kilometer (1,800 mi) front, the largest invasion force in the history of warfare. In addition to troops, the Wehrmacht employed some 600,000 motor vehicles and between 600,000 and 700,000 horses. The offensive marked the beginning of the escalation of the war.

Operationally, the German forces achieved surprising victories and occupied some of the most important economic areas of the Soviet Union, mainly in Ukraine, and inflicted, as well as sustained, heavy casualties. Despite their successes, the German offensive stalled in the Battle of Moscow and was subsequently pushed back by the Soviet winter counteroffensive. The Red Army repelled the Wehrmacht's strongest blows and forced the unprepared Germans into a war of attrition. The Wehrmacht would never again mount a simultaneous offensive along the entire strategic Soviet–Axis front. The failure of the operation drove Hitler to demand further operations of increasingly limited scope inside the Soviet Union, all of which eventually failed.

The failure of Operation Barbarossa was a turning point in the fortunes of the Third Reich. Most importantly, the operation opened up the Eastern Front, to which more forces were committed than in any other theater of war in world history. The Eastern Front became the site of some of the largest battles, most horrific atrocities, and highest casualties for Soviets and Germans alike, all of which influenced the course of both World War II and the subsequent history of the 20th century. The German armies captured 5,000,000 Soviet prisoners of war who were not granted protections stipulated in the Geneva Conventions. A majority of them never returned alive. The Nazis deliberately starved 3.1 million of the prisoners to death as part of a "Hunger Plan" that aimed to reduce the population of Eastern Europe and then re-populate it with ethnic Germans. Over a million Soviet Jews were murdered by Einsatzgruppen death squads and gassing as part of the Holocaust.