Edited sentence: At that time Germany was completely dependent on Romanian oil and could not fight the war without them.Germans attempts to capture Stalingrad and cut off the Soviet Unions source of oil failed and the soviets captured much of Eastern Europe and part of Germany.It became clear that such an attack would have to be very large until it took all the resources of the German military.It prevented a complete takeover of Europe by the Soviet Union but did not cause the communist government to collapse.Operation Barbarossa was not a complete failure but neither did it succeed.The Soviet Union was waiting for Germany to begin its invasion of England.The non-aggression pact between Germany and the Soviet Union was signed to prevent such a situation.The only reason to attack the Soviet Union in 1941 would be if the Soviet Union was planning to invade Romania and take over the oil fields.The only way to cause the Soviet Union to withdraw from Romania was to attack and force her to move troops to defend against such an attack.There would be no one to defend against a Soviet invasion, Germany had outlawed all political parties and armies in Europe.These historians, however, are unable to explain why Germany would invade the Soviet Union before the war in the west was over and open a second front.They realized where the threat was coming from but by that time it was to late.When that occurred all of Europe would be in extreme danger