[1] Heiskanen joined the Jaeger Movement in 1915 and trained and fought in the Royal Prussian 27th Jäger Battalion.
Heiskanen was released next year during the October Revolution, and he returned to Finland.
Heiskanen commanded the IV Corps during first days of the Winter War.
[2] During the Continuation War, Heiskanen was the Commandant of Viipuri, and the General Inspector of the Military Training.
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