Final answer:
During the Cold War, President Truman used diplomacy to contain communism and formed NATO for defense against communist aggression.
Step-by-step explanation:
During the Cold War, President Truman stated that the United States would use diplomacy to contain communism. This meant that the U.S. would use peaceful negotiations and agreements with other countries to prevent the spread of communism. The U.S. also formed NATO (North Atlantic Treaty Organization), a military alliance, to defend against any aggression from communist countries.
Learn more about Containment of communism during the Cold War