What does truman mean when he claims," should we fail to aid greece and turkey in this fateful hour, the effect will be far reaching to the west as well as to the east"?

By the given statement in question, Truman wanted to imply that the effect of communism was growing and if it could not be checked by aiding such countries as Greece and Turkey, then it would have far reaching effects. Truman feared that communism would slowly grip these countries in financial trouble and spread to the Latin American countries and the countries in the East at a very fast rate. 

Is there like something i’m supposed to cite because i don’t see any background information?