The correct answer is: "Truman Doctrine"
The Truman Doctrine was the name given to the containment policy that the US adopted after WWII, a foreign affairs approach which focused on stopping the spread of communism worldwide. This is why the US started the Marshall Plan initiative, and sent financial aid to help rebuild Western European countries, in order to set an alliance with them against the expansion of the URSS that had already turned many Eastern European countries into Soviet republics, soon after the end of WWII.