The enemy of my enemy is my friend

The enemy of my enemy is my friend is an ancient proverb which suggests that two opposing parties can or should work together against a common enemy. The earliest known expression of this concept is found in a Sanskrit treatise on statecraft, the Arthashastra, which dates to around the 4th century BC, while the first recorded use of the current English version came in 1884.

The proverb is sometimes phrased as "the enemy of mine enemy is my friend" or "my enemy's enemy is my friend."

In his Arthashastra: Book VI, "The Source of Sovereign States", Kautilya writes:

The king who is situated anywhere immediately on the circumference of the conqueror's territory is termed the enemy.
The king who is likewise situated close to the enemy, but separated from the conqueror only by the enemy, is termed the friend (of the conqueror).

The idea that "the enemy of my enemy is my friend" functioned in various guises as foreign policy by Allied powers during the Second World War. In Europe, tension was common between the Western Allies and the Soviet Union. Despite their inherent differences, they recognized a need to work together to meet the threat of Nazi aggression under the leadership of Adolf Hitler. Both U.S. President Franklin D. Roosevelt and British Prime Minister Winston Churchill were wary of the Soviet Union under the leadership of Joseph Stalin. However, both developed policies with an understanding that Soviet cooperation was necessary for the Allied war effort to succeed. There is a made to his personal secretary John Colville on the eve of Germany's invasion of the Soviet Union (Operation Barbarossa). He was quoted as saying, "if Hitler invaded Hell, I would make at least a favourable reference to the Devil in the House of Commons." The Soviet leader reciprocated these feelings towards his Western allies. He was distrustful and feared that they would negotiate a separate peace with Nazi Germany. However, he also viewed their assistance as critical in resisting the Nazi invasion.

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