Central Treaty Organization
After graduating from the National War College in 1950, Porter held a variety of positions to include commander, 2nd Armored Cavalry Regiment; Deputy G-3, Allied Land Forces Central Europe; Chief of Staff, X Corps; member of the National Security Council Planning Board; Commander, 3rd Armored Division; United States Representative to the Permanent Deputies Group, Central Treaty Organization. From April 1964 to 1965 he commanded the First United States Army at Fort Jay, Governors Island, New York. His final assignment was Commander-in-Chief, United States Southern Command.