The armies of Nazi Germany invaded the Soviet Union on 22 June 1941. Onilova volunteered for service in the Red Army when the Siege of Odessa commenced in August 1941. She was originally made a medic in 54th Rifle Regiment in the 25th Rifle Division of the Separate Coastal Army, but soon used her prewar training to prove herself as a gunner when she picked up her comrades' jammed machine gun, quickly cleared it, and used it to repulse a detachment of advancing Germans.
