The most important similarity between the Truman Doctrine and the Marshall Plan is:
Both programs aided other countries’ economies to help the countries rebuild after World War II.
While the Truman Doctrine primarily focused on containing the spread of communism through military and political support, the Marshall Plan was an economic aid program designed to help rebuild European economies. Both strategies were part of the broader U.S. response to the challenges posed by the Soviet Union in the post-war period.