PVA casualties during the first 12 months of the Korean War, from October 1950 to October 1951, were heavy. Soviet material support was slight, and because the only available means to transport supplies into Korea for the first year of the war was a force of 700,000 labourers, all available supplies were light and limited. The UN forces also had complete air superiority. The logistic constraints later caused 45,000 Chinese soldiers to freeze to death between November 27 and December 12, 1950 because of inadequate winter clothing. China's insufficient artillery, armor, and air support meant that Peng was forced to rely heavily on human wave tactics until the summer of 1951. Stealthy fireteams attacked in column against weak points in enemy defenses in the hope that surprise, attrition, and perseverance would break the enemy lines. Participants even drank large quantities of Kaoliang wine to improve their courage. Some of the worst Chinese battle losses occurred during the Second and the Fifth Phase Campaign. Up to 40% of all Chinese forces in Korea were rendered combat ineffective between November 25 and December 24, 1950, and about 12 Chinese divisions were lost in from April 22 to June 10, 1951. All in all, over a million Chinese soldiers became casualties during the course of the war. Peng justified the PVA's high casualty rate by his almost religious belief in communism and the party and his belief that the ends of the conflict justified the means. Some accounts even claimed that Peng invented the human wave tactic under the name "short attack" to exploit his manpower advantage.