In 1918, he took part in the Finnish Civil War as a lieutenant of the White side. Among many of his known accomplishments, General Raappana was chosen to command the Finnish detachment - nicknamed "Group Raappana" ("Ryhmä Raappana" in Finnish) - that was to stop the enemy in the very final Finnish-Soviet battle during World War II.
In 1918, he served as a lieutenant on the White side during the Finnish Civil War. Among his significant accomplishments was commanding the Finnish detachment known as "Group Raappana" ("Ryhmä Raappana" in Finnish), which sought to stop the enemy in the decisive final battle between Finland and the Soviet Union during World War II.