One of President Truman's most significant actions was the "Truman Doctrine." This doctrine was an attempt by the United States to help rebuild Europe after the destruction that it suffered during World War II. However, it is difficult to state how much of this was a consequence of Truman wanting to protect people in other countries and how much was a desire to protect Americans.
I believe that Truman was mostly guided by a desire to protect America. Truman believed that by helping Europe recover, the United States would be able to maintain a good economy, as this would allow the country to maintain international trade. Moreover, Truman believed that by giving such foreign aid, he would be more successful in keeping communism at bay. Both of these reasons were influential in developing the Truman Doctrine.