Fear. External & Internal Fear. From 1946-through the decade of the 1950s, Americans were fearful of outside threats, such as a Soviet nuclear attack, and inside threats, such as loss of a career or a marriage due to an accusation of being a communist.
But we begin with external threats, and the the national security policy called "Containment."
Understanding this Unit means understanding the concept of "containment." This theory will be applied politically, economically, and militarily.
Political: The Truman Doctrine
Economically: The Marshall Plan