He was one of the Finnish Jaeger troops trained in the volunteer Royal Prussian 27th Jäger Battalion between 1915 and 1918.

During the Finnish Civil War he served as a battalion commander in the battles of Tampere and Viipuri.

[1] During the Continuation War he commanded the Army of Karelia until January 1942, after which he was again appointed the Chief of the General Staff.

After the war he served as the Army's commander-in-chief but was forced to resign because of the Weapons Cache Case.

[1] Heinrichs was one of the military experts of the delegation sent by president Paasikivi to Moscow for the Agreement of Friendship, Cooperation, and Mutual Assistance in 1948.