Final answer:
The containment policy was a U.S. strategy to prevent the spread of Soviet influence and communism, based on George F. Kennan's advice in the 'Long Telegram'.
Step-by-step explanation:
The containment policy during the Cold War was a strategic approach adopted by the United States to prevent the expansion of Soviet influence and the spread of communism beyond the Eastern European countries that were already under its control. This policy was a central aspect of the United States' foreign relations and military strategies which spanned over three decades. American diplomat George F. Kennan was integral in formulating this approach with his 'Long Telegram,' which advised that Soviet expansion should be restricted to its current borders, anticipating that the communist system would eventually fall apart internally.