During the Russian Civil War he sided with the White movement and fought against the Bolsheviks, notably as the last chief of staff of Kornilov Division of the Army of General Wrangel.
During World War II, as an ardent anti-communist he sided with the Axis powers and the Russian Liberation Movement, and briefly served in the propaganda services of the Wehrmacht as head of the Russian section.
In early 1945, Messner returned to active front-line service as a Major in Boris Smyslovsky's 1st Russian National Army.
Through Liechtenstein Messner and his family moved in 1947 to Argentina, where he continued his earlier work as a journalist, publisher, writer and military theorist.
Messner's most well-known publication, "Mutiny, or the name of the Third World War" (Russian: Мятеж — имя третьей всемирной), predicted that the future wars would be waged by small terrorist cells and special forces, gaining influence by subversion and organised revolutions rather than through traditional warfare.