The Winter Offensive was a major Pacific War military offensive from November 1925-March 1926, led by the Chinese Imperial Army against the Allies in Northern Asia. The fighting involved an all-out invasion of Siberia by six and a half million Chinese soldiers - almost a third of the entire Imperial Army, with strategic support from 725,000 Korean soldiers in the east and 400,000 Japanese soldiers arriving from Kamchatka. Despite overwhelming numbers, the Asian Powers were unprepared for winter conditions, conditions under which the Siberian Army, depleted and starving, excelled at. With starvation, guerrilla attacks, frostbite and severed supply lines deepening the attrition on the Chinese side, the Winter Offensive collapsed by late February of 1926 and the Chinese withdrew beyond the Selenga River in March. While there would be a renewed Chinese offensive in summer 1926, fighting in Western Siberia had ended, for all practical purposes.
The Winter Offensive resulted in the largest single loss of human life during a military campaign in recorded history, with nearly three million deaths on the Chinese side, most from starvation and cold. Supportive Asian Powers losses included 388,000 Korean deaths and 118,000 Japanese deaths, with nonfatal casualties for all three Asian participants estimated at three and a half million. The most devastating losses came from the Western Theater, where the Chinese Third Imperial Army, 975,000 strong at its outset, returned from Omsk in April of 1926 with only 88,000 men remaining, few of whom were in a condition to fight afterwards.
The Siberians suffered 550,000 dead, the Alaskans 310,000, and the Americans 112,000, with Allied non-fatal casualties at an estimated one and a half million. The failure of the Winter Offensive is regarded as a turning point in the Northern Front, after which the Chinese would never again seriously threaten major Siberian population centers, and all Asian Powers tactical victories would occur in the more sparsely populated eastern end of the Northern Front, where they could rely on Korean and Japanese support.