The following year, on 1 January 1942, representatives of thirty nations formally at war with the Axis powers—led by the "Big Four" powers of China, the Soviet Union, the U.K., and the U.S.—signed the Declaration by United Nations, which formalized the anti-Axis alliance and reaffirmed the purposes and principles of the Atlantic Charter. The following day, representatives of twenty-two other nations added their signatures. The term "United Nations" became synonymous with the Allies for the duration of the war, and was considered the formal name under which they were fighting. The Declaration by United Nations formed the basis of the United Nations Charter; virtually all nations that acceded to it would be invited to take part in the 1945 San Francisco Conference to discuss and prepare the Charter.