[1][2][3] Following the school, he was attached to the Marine detachment aboard the newly commissioned battleship USS Louisiana and sailed to Cuba in order to suppress armed revolt of independence war veterans who defeated the meager government forces.

While aboard the Louisiana, Keyser took part in the voyage around the world with the stops in Port of Spain, Rio de Janeiro, Punta Arenas, Melbourne, Sydney, Auckland, Manila, Yokohama, Singapore, entering the Indian Ocean in December 1908; they coaled in Colombo and passed through the Suez Canal with another stops in Port Said, Gibraltar, and finally returned to Hampton Roads on 22 February 1909.

He was promoted to the rank of captain in September 1916 and assumed duty as aide to the commandant of the Marine Corps, George Barnett.

Keyser subsequently joined 5th Marine Regiment and assumed duty as executive officer of 2nd Battalion under Lieutenant Colonel Frederic M.

Keyser was slightly wounded on July 20 and ordered back to the staff od 2nd Army Division, now commanded by Marine Major General John A. Lejeune.

[4] Keyser remained on the staff of 2nd Army Division during the Meuse-Argonne Offensive and following the Armistice in November 1918, took part in the Occupation of the Rhineland in Coblenz.

[4] Keyser returned to the United States with the rest of Fourth Marine Brigade in August 1919 and assumed duty with the recruiting office in Atlanta, Georgia.

[1][2][8][9] He was ordered back to the United States in August 1925 and served at the Headquarters Marine Corps in Washington, D.C., with the section of Operations and Training until April 1930.

[1] His tour of duty at Headquarters Marine Corps ended in June 1936, and Keyser requested retirement, which was granted on February 1, 1937.

[1][2] Keyser was contacted by his old friend, now Commandant of the Marine Corps, Thomas Holcomb in March 1941 and asked whether he would return to active duty.

But Keyser's heart condition forced him to leave the office in May of that year, and he was ordered to the Naval hospital in Bethesda for treatment.

He was not called back to active duty for the duration of the war and was also promoted to the rank of major general on the retired list for having been specially commended in combat.