Harry S. Truman's foreign policy was primarily focused on which of the following?

Harry S. Truman's foreign policy was primarily focused on the containment of communism, which refers to the strategy to prevent the spread of communism beyond where it already existed, particularly in Europe and Asia after World War II. This approach was articulated through several key policies and doctrines, most notably the Truman Doctrine established in 1947, which aimed to provide support to countries resisting communist insurgencies or influence.

The emphasis on containment reflected the geopolitical landscape of the time, characterized by the growing power of the Soviet Union and the perceived threat of communism to democratic nations worldwide. Truman's implementation of the Marshall Plan to aid European recovery and the establishment of NATO were further extensions of this containment strategy, as they sought to economically and militarily strengthen countries against potential communist expansion.

In this context, the other options do not accurately portray Truman's foreign policy. Isolationism, expansionism, and neutrality do not capture the active and interventionist stance that characterized his administration. Thus, the focus on containment is central to understanding Truman's role in the early Cold War era.