In March 1920, Richardson returned to his permanent regular grade of Captain. On August 9, 1920 Captain Richardson joined the Office of the Chief of Cavalry until January 28, 1921, when he returned for his third Philippine tour of duty. In the Philippines, soon to be Major Richardson served as Assistant to the Assistant Chief of Staff for Operations, Headquarters, Philippine Department, Manila until April 6, 1923, when he returned to the United States to attend the Command and General Staff School at Fort Leavenworth, Kansas. Upon graduation in June 1924, Major Richardson sailed for France to attend the Ecole Superieure de Guerre, Paris, and upon graduation on September 2, 1926, he was ordered to Rome, Italy to serve as Military Attaché. In March 1928, newly promoted Lt. Colonel Richardson returned to the United States to join the 13th Cavalry at Fort Riley, Kansas. On August 20, 1928, he was again assigned to West Point as Commanding Officer, Provisional Battalion and Executive Officer until March 2, 1929, when he became Commandant of Cadets and Head of Department of Tactics. On June 30, 1933, he attended the Army War College, Washington, D.C., and upon graduation he served in the Military Intelligence Division, War Department General Staff until December 7, 1935. Soon to be promoted to Colonel, he was given command of 5th Cavalry at Fort Clark, Texas. In June 1938, Colonel Richardson assumed command of the 2nd Cavalry Brigade at Fort Bliss, Texas. On October 10, 1940, he assumed command of the 1st Cavalry Division, Fort Bliss, Texas. On February 11, 1941, he became the Director of Public Relations, Washington, D.C. At the start of World War II and the Pearl Harbor bombing, then Major General Richardson commanded Seventh Corps Area where he oversaw the buildup of US California defenses following the Pearl Harbor bombing. Several months after Pearl Harbor, General Marshall sent him out on a personal reconnaissance of the whole Pacific theater to assess the extent of the allied situation. While in Australia, General MacArthur, his USMA classmate, requested of General Marshall that Gen Richardson return to command the Army Corps being stood up in Australia. Upon his return to Washington, Gen Richardson frankly reported to Gen Marshall the inappropriateness of US forces being placed under the command of foreign officers. This was based on his World War I experience from Gen Pershing insisting that US Forces fight under US command. This led to the unconfirmed rumor that his report cost him the Corps command under Gen MacArthur.