During the Winter War (1939–1940) between Finland and the Soviet Union, Häyhä served as a sniper for the Finnish Army against the Red Army in the 6th Company of JR 34 during the Battle of Kollaa. In temperatures between −40 °C (−40 °F) and −20 °C (−4 °F), dressed completely in white camouflage, Häyhä was credited with 705 confirmed kills of Soviet soldiers. A daily account of the kills at Kollaa was made for the Finnish snipers. All of Häyhä's kills were accomplished in fewer than 100 days – an average of just over five kills per day – at a time of year with very few daylight hours.