Shortly after his appointment to the Historical Section, Nicholson was appointed as the narrator for Pacific Command. In the wake of Operation Cottage in August 1943, he traveled in U. S. Army aircraft through the Aleutian Islands. While covering the Pacific, Nicholson was a passenger in the first American plane to land on Kiska after its capture from the Japanese. Following the cessation of hostilities in September 1945, in early 1946, new Director of the Historical Section Colonel C. P. Stacey (1906–1989) appointed Nicholson the Officer-in-Charge of the Historical Section at Canadian Military Headquarters in London. During his time in London, Nicholson gathered documents pertaining to Canada's role in the Battle of Hong Kong of December 1941. This work resulted in the 1946 pamphlet entitled "Canadian Participation in the Defence of Hong Kong, December 1941". In 1947, Nicholson returned to Canada where he was appointed Deputy Director of the Historical Section, Army Headquarters, Ottawa.