A beginning of the “Barbarossa” Operation, the Nazi Germany's invasion of the Soviet Union, its former ally. Planning for Operation Barbarossa started in 1940 and the invasion plan was confirmed by Hitler on September 18, 1940 (Directive no. 21). The invasion opened a new phase of World War II and led to a broadening of the anti-fascist coalition.
Initially Soviet Army - poorly trained and lacked of experienced officers (many Soviet generals and officers were killed during Stalinist repressions in 1937-1938) - suffered huge losses. German troops gained large territories of Belarus, Ukraine, Baltic states and approached Moscow.