The Truman Doctrine stated that the United States was to adopt a policy of supporting countries that are being threatened by communism. This changed American foreign policy; the United States was no longer going to isolate itself from the rest of the world, they would "not let communism set its foot outside of its current borders". This would be done by setting up a buffer zone of friendly, non-communist governments around the Soviet Union, preventing it from expanding its communist ideals. The way to get these friendly governments was to come later, via the Marshall plan.