An Enemy of My Enemy is My Friend (U.S. and Soviet Relations in WW2)
There goes a saying, “An enemy of my enemy is my friend.” Before World War 2, many never would have imagined that the United States and the Soviet Union would fom an alliance. The Cold War between the two great nations was in progress and the two had radially different beliefs. In addition, the Soviet Union signed a non-aggression pact with Nazi Germany, occupied Eastern Poland and waged a “Winter War” against Finland, all of which the U.S. strongly disapproved. From a networks standpoint, the edge, U.S./Soviet relations, between the nodes, the U.S. and Soviet Union, was negative.
Yet, when Nazi Germany enters the picture, one can see a change in the positivity and negativity of the edges. With the invasion of Soviet Union by Nazi Germany, the U.S. and Soviet Union were able to forge and alliance. The United States was not fond of both Germany and the Soviets, but viewed Germany as a greater threat to world peace and was willing to cooperate with the Soviets to stop Russia. When Germany dishonored its non-aggression pact with the Soviets, the U.S. had the perfect opportunity to strike up an alliance. By invading the Soviets, Germany made itself an enemy of the Soviets. Therefore, because Russia now viewed Germany as an enemy and the U.S. viewed Germany as a greater enemy than it did the Soviets, the U.S. and Soviet Union were able to forge an alliance. Similarly, from a Soviet standpoint, the U.S. was already enemies with Germany and the Soviets were neutral with Germany. With the German invasion of the Soviet Union, the Soviets now viewed Germany as an enemy. With a common enemy, the Soviet Union and U.S. were able to forge an alliance to maintain structural balance.
Source: https://history.state.gov/milestones/1937-1945/us-soviet