As a colonel Siilasvuo lead the Finnish defence at Kuhmo and in the Battle of Suomussalmi.
During the Continuation war he lead the III Corps in northern Finland in 1941 and on the Karelian Isthmus in 1944. After the peace with the Soviets, he was given the command of the Finnish forces fighting the Germans in Lapland.
He was awarded the Mannerheim Cross on December 21 1944.
His son Ensio Siilasvuo is also a general in the Finnish army.