[Dean Acheson] played a central role in defining American foreign policy during the Cold War. He likewise played a central role in the creation of many important institutions, including Lend Lease, the Truman Doctrine, the Marshall Plan, the North Atlantic Treaty Organization [NATO], the International Monetary Fund, and the World Bank, together with the early organizations that later became the European Union and the World Trade Organization. His most famous decision was convincing Truman to intervene, in June 1950, in the Korean War. Historians have argued, "Dean Acheson was more than 'present at the creation' of the Cold War; he was a primary architect."

Acheson came under heavy attack for his policies in China and for his defense of State Department employees accused during Senator Joseph McCarthy's anti-Communist investigations. Acheson was instrumental in framing U.S. policy toward Vietnam, persuading Truman to dispatch aid and advisors to French forces in Indochina, though in 1968 he finally counseled President Lyndon B. Johnson to negotiate for peace with North Vietnam. During the Cuban Missile Crisis, President John F. Kennedy called upon Acheson for advice, bringing him into the executive committee (ExComm), a strategic advisory group.