Piriyev was drafted into the Red Army in October 1941. He fought in combat from May 1942. His first action was fought on the Southern Front during the retreat in the Battle of the Caucasus. In February 1943 he fought in the Novorossiysk-Maikop Offensive and reportedly destroyed a German machine gun with a hand grenade. He fought in the Malaya Zemlya for seven months. In September 1943 he participated in the Kerch–Eltigen Operation.