Returning to the United States in April 1919, Smith's assignments in the next four years included duty at Norfolk, Virginia, study at the Naval War College, Newport, Rhode Island, and service in Washington, D.C., with the War Plans Section of the Office of Naval Operations. There, he was the first Marine officer to serve on the Joint Army-Navy Planning Committee. Leaving Washington in May 1923, he served aboard the battleships and as Fleet Marine Officer, U.S. Scouting Fleet, until September of that year. In February 1924, after serving at Marine Corps Headquarters and in the West Indies in connection with joint Army-Navy maneuvers, Smith joined the Marine Brigade on expeditionary duty in Haiti, serving as that unit's chief of staff and officer in charge of operations and training. He returned from that country in August 1925, to serve as chief of staff of the 1st Marine Brigade at Quantico, Virginia, until September 1926, as a student in the Marine Corps School, Quantico, from then until June 1927, and as post quartermaster of the Marine Barracks, Philadelphia Navy Yard, from July 1927 to March 1931. In April 1931, Smith began another tour of sea duty, this time aboard the as aide to the commander and Force Marine Officer of the Battle Force, U.S. Fleet. He served in those capacities until June 1933, commanded the Marine barracks at the Washington Navy Yard from then until January 1935, and served the following two years at San Francisco, California, as chief of staff, Department of the Pacific. From there he was ordered to Marine Corps Headquarters in March 1937, to serve two years as director of the Division of Operations and Training, after which he was assistant commandant of the Marine Corps under Major General Thomas Holcomb from April to September 1939. After the latter assignment, General Smith assumed command of the 1st Marine Brigade at Quantico, taking that unit to Guantanamo Bay, Cuba, for extended amphibious training in October 1940. In February 1941, when the brigade was redesignated the U.S. 1st Marine Division, he became that organization's first commander. He returned with the division to Quantico in April 1941, and in June of that year he was detached from it to take command of the organization that eventually became the Amphibious Force, Atlantic Fleet. Under this command, the 1st Marine Division and the 1st and 9th Army Divisions received their initial training in amphibious warfare. Moving to San Diego in August 1942, the general took command of the Amphibious Corps, Pacific Fleet, under which he completed the amphibious indoctrination of the 2d and 3d Marine Divisions before they went overseas, and the 7th Army Division and other units involved in the Aleutians operation.