Seventy years ago, President Harry Truman laid out his vision for U.S. foreign policy in a speech that became known as "The Truman Doctrine." It marked the start of the Cold War, with the U.S. assuming a role as a global leader. A straight-talker with little political experience, Truman is sometimes compared to President Trump. But Trump's doctrine of "America First" marks a departure from previous foreign policy. We examine the events leading up to Truman's speech, it's influence on U.S. foreign policy, nationalism, and global involvement.