A doctrine developed by Truman under the containment policy that promised economic aid to those fighting communists. The doctrine would dragged the U.S into more conflicts like the Vietnam and Korean wars. Under this doctrine the U.S. received $400 gave to help Greece and turkey from becoming communist, because they were very poor and the U.S. feared that this type of government would be appealing to them.
After the war Europe was a mess, they had food shortages and they were in bad debt. The U.S didn't want theses states to become communist so George Marshall created the Marshall Plan were the U.S would help Europe recover with economic aid.