Kaitseliit
In 1917 Õunapuu formed a Student Home Guard Squad, which consisted of 340 of his students, of which 82 were boy scouts. Õunapuu's squad protected Estonian Salvation Committee on 24 February 1918 during the proclamation of Estonian Independence. During the German Occupation Õunapuu organized an underground squad of Estonian Defence League. On 16 December 1918 he was promoted to serve as the commander of the pioneer company of Kalevlaste Malev. He was wounded in the battle of Järveküla, near Narva.