Tuhia tētahi tohutoro mō tēnei wāhanga - Ko Aarnio he tūmanako ki te White Guards i te Savonia Front i te Pakanga ā-Iwi Finnish. I muri mai ka uru ia ki te Pakanga Independence o Estonia, te Pakanga Independence o Latvia me te haerenga a Aunus
i te Rāwhiti o Karelia. I whakawhitihia a Aarnio mai i te mahi hōia ki te ope hoia i te tau 1920. I puta ia i te Kadettikoulu i te 1926 me te Sotakorkeakoulu i te 1933. I whakatairangahia a Aarnio hei rangatira i te 1929 ka mahi i te tari hononga o waho o te General Staff.