Shepherd returned to the States in December 1920, and was assigned as
White House aide and aide-de-camp to the commandant of the Marine Corps, Major General
John A. Lejeune. In July 1922, he took command of a selected company of Marines at the
Brazil's Centennial Exposition in
Rio de Janeiro. In June 1923, Shepherd was ordered to sea duty as commanding officer of the
Marine Detachment on the . This tour was followed by duty at the Marine Barracks, Norfolk, where he commanded the Sea School. In April 1927, Shepherd sailed for expeditionary duty in China, where he served in the
3rd Marine Brigade in
Tientsin and
Shanghai. Shepherd returned to the United States in 1929 and attended the Field Officers' Course, Marine Corps Schools. After graduation Captain Shepherd was assigned overseas again, this time on detached duty with the
Garde d'Haïti, serving for four years as a district and department commander in the
United States occupation of Haiti. Following the withdrawal of Marines from Haiti in 1934, Shepherd was detailed to the Marine Barracks, Washington, D.C., as executive officer and as registrar of the Marine Corps Institute. Following graduation in May 1937 from the
Naval War College at
Newport, Rhode Island, Shepherd commanded the
2nd Battalion, 5th Marine Regiment, part of the newly formed
Fleet Marine Force (FMF), Atlantic, which was being extensively employed in the development of amphibious tactics and techniques. In June 1939, Shepherd was ordered to the Staff of
Marine Corps Schools,
Quantico, Virginia, where he served during the next three years as director, Correspondence School; chief of the Tactical Section; officer in charge of the Candidates Class; and assistant commandant. ==World War II==