Final answer:
George Kennan developed the policy of containment while serving as an advisor to President Truman. This approach influenced U.S. foreign policy throughout the Cold War, aiming to restrict Soviet influence to current borders, and was integral to maintaining a stance against the spread of communism.
Step-by-step explanation:
The developer of the idea of containment was George Kennan, a Princeton-trained historian, and diplomat who sent a crucial document known as the "Long Telegram" outlining his views on the Soviet Union and the strategies the United States should adopt.
Kennan advised that the best way to counter Soviet plans for expansion was through a policy of containment, primarily through economic means, to limit Soviet influence to where it already existed and prevent its political spread into new regions. This approach laid the groundwork for U.S. foreign policy during the Cold War.
Containment was integral to the Truman administration's foreign policy, emphasizing the need to prevent the spread of communism beyond the so-called "iron curtain" of Eastern Europe. The policy would shape the country's international relations and military decisions for over three decades, influencing subsequent administrations, including that of President Dwight D. Eisenhower, who endorsed and expanded upon the containment strategy through the concept of brinkmanship.