When the Korean War broke out, Holcomb was transferred to the 1st Marine Division staff and appointed the Intelligence Officer (G-2) under Major General Oliver P. Smith. He participated in the Battle of Pusan Perimeter, the Battle of Inchon or Battle of Chosin Reservoir, and in the interrogation of Chinese prisoners of war, with whom he worked with in China during World War II. Holcomb was also decorated with his second Legion of Merit for his service as 1st Division's intelligence officer.