How was the truman doctrine a change in previous us foreign policy? a: the truman doctrine was a shift from isolationist policy because the belief that it was the us’ responsibility to stop the spread of communism to weaker countries around the world b: the truman doctrine encouraged the us to “speak softly and carry a big stick” c: the truman doctrine aimed to decrease military spending and increase the national surplus d: the truman doctrine encouraged the us to withdraw itself from world affairs and let countries sort out their own differences