On June 22, 1941, Nazi Germany and its Axis allies began a massive invasion of the Soviet Union named Operation Barbarossa - some 4.5 million troops launched a surprise attack deployed from German-controlled Poland, Finland, and Romania. Hitler had his eyes on Soviet resources even after Germany and the USSR signed a non-aggression pact in 1939. Both sides had long been suspicious of one another and the agreement merely gave them more time to prepare for a probable war. The Soviets were unprepared for the sudden blitzkreig attacks across a border that spanned nearly 2,900 km (1,800 mi), and suffered horrible losses. Within a single week, German forces advanced 200 miles into Soviet territory, destroyed nearly 4,000 aircraft, and killed, captured, or wounded some 600,000 Red Army troops. By December of 1941, Germany had advanced to within sight of Moscow, and laid siege to the city, but the notorious Russian winter set in (nicknamed "General Winter", and German advances came to a halt. At the end of this, one of the largest, deadliest military operations in history, Germany had suffered some 775,000 casualties, more than 800,000 Soviets had been killed, and an additional 6 million Soviet soldiers were wounded or captured. The operation was also a failure for Germany -- despite massive advances, Hitler's plan to conquer the Soviet Union before winter had failed, at great cost, which would prove to be a turning point in the war.