The Korean War was a conflict between the United States and its United Nations allies and the communist powers under influence of the Soviet Union (also a UN member nation) and the People's Republic of China (which later also gained UN membership). The principal combatants were North and South Korea. Principal allies of South Korea included the United States, Canada, Australia, the United Kingdom, although many other nations sent troops under the aegis of the United Nations. Allies of North Korea included the People's Republic of China, which supplied military forces, and the Soviet Union, which supplied combat advisors and aircraft pilots, as well as arms, for the Chinese and North Korean troops.
Which two countries were the primary fighters for territory in the Japanese War?