Excellent answer.  The Marshall Plan, the brainchild of George C. Marshall (who had been head of the Allied Chiefs of Staff during WW II), really had no intended connection to the Truman Doctrine and the policy of "Containment."  It did, however, bring the US and USSR into conflict over the rebuilding of Germany and the western sectors of Berlin, and so became entangled in the Containment Policy, which was the invention of George Keenan.  By rebuilding Western Europe and seeking to prevent the spread of Communism by all means possible, not only military means, the two policies became for a time two integral parts of Truman's foreign policy.  The Marshall Plan, of course, ended when it's purpose was finished, but Containment remained a vital part of US policy until the economic collapse of the Soviet Union.  That economic collapse was the very point of Keenan's plan.