Germany’s need for oil was a major factor in Hitler’s decision to invade Russia in 1941: Operation Barbarossa, launched on 22 June, involved 3.8 million Axis personnel in the largest military invasion in history. But as Barbarossa misfired in the winter of 1941, and as Soviet counter-offensives eliminated the immediate threat to Moscow, oil remained crucial in formulating German strategy for the following year.
In September 1939, German oil reserves had totalled 842,000 tons. The subsequent conquest of much of Western Europe added another 280,000 tons of captured oil, and imports from the Soviet Union a further 225,000 tons. However, a study of May 1941 found that reserves would be exhausted by August of that year, as military requirements surpassed imports and home production.