George Kennan, a prominent American diplomat and historian, argued that the United States could slow Russia's expansive tendencies through a policy of "containment." Kennan believed that the Soviet Union's expansionist agenda was driven by its internal ideology and the desire for security, and that the US needed to contain Soviet influence and prevent its spread to other countries.
In his famous "Long Telegram" sent in 1946, Kennan suggested that the US should adopt a policy of "patient but firm and vigilant containment" of Soviet expansionism. This would involve using diplomatic, economic, and military means to prevent the spread of communism and Soviet influence, while also building up the US military and economic strength to deter Soviet aggression.
Kennan argued that the US needed to avoid direct military confrontation with the Soviet Union, but should instead rely on a policy of strategic containment to limit Soviet expansionism and eventually cause the Soviet system to collapse from within.
Overall, Kennan's ideas on containment had a significant impact on US foreign policy during the Cold War, and were influential in shaping the US response to Soviet expansionism for decades to come.