In 1898 Holcomb took a job as a cost clerk at the Bethlehem Steel works in Sparrows Point, Maryland, for two years.

Holcomb first claim to fame was winning the International long distance rifle championship in 1902 Montreal, Canada.

He was promoted to first lieutenant March 3, 1903 and put in charge of the US Marine Corps rifle team bringing to championship in 1911.

He continued on duty in Peking as attache on the staff of the American Minister for study of the Chinese language and remained until May 1911.

The French Government conferred on him the Cross of the Legion of Honor and three times awarded him the Croix de Guerre with Palm.

From August 1927 to February 1930, Col Holcomb commanded the Marine detachment, American Legation, Peking, China.

From June 1932 to January 1935, prior to his appointment to brigadier general, he served in the Office of Naval Operations, Navy Department.

"[7] In 1943, he passed Letter of Instruction 421, which restricted African-American Marines' ability to be promoted and prevented them from serving as non-commissioned officers in charge of whites.

Because he had been specially commended for his performance of duty in actual combat, he was advanced one rank on the retired list in accordance with a newly passed Act of Congress.

Citation: The President of the United States of America takes pleasure in presenting the Navy Cross to Lieutenant Colonel Thomas Holcomb (MCSN: 0-436), United States Marine Corps, for extraordinary heroism while serving with the Second Battalion, 6th Regiment (Marines), 2d Division, A.E.F.

As Commander of the Second Battalion, and later as second-in-command of the 6th Regiment (Marines), Lieutenant Colonel Holcomb performed all of his duty in a most commendable manner, proved himself a brave, active, resourceful officer by his zealous and intelligent attention to duty as well as personal courage and fearlessness in the face of the enemy.

[11]On March 9, 1944, President Roosevelt nominated Gen Holcomb for the position of United States Minister to the Union of South Africa.

[12] This article incorporates public domain material from websites or documents of the United States Marine Corps.