Fifty-one years ago today, on February 22, 1974 (February 1, 1974 in the lunar calendar), Mao Zedong put forward the theory of "three worlds". Mao Zedong met with Zambian President Kaunda in 1970s. The world situation has changed dramatically, and there has been a situation of great turmoil and reorganization. Under such circumstances, what diplomatic strategy should China adopt? When Chairman Mao Zedong met with Zambian President Kaunda on February 22, 1974, he put forward the theory of dividing the three worlds and called for unity against hegemonism. Chairman Mao Zedong said, "I think the United States and the Soviet Union are the first world. Centrists, Japan, Europe and Canada, are the second world. We are the third world" and "the third world has a large population. Asia is the third world except Japan. The whole of Africa is the third world, and Latin America is the third world." This strategic thought has rich contents and great practical guiding significance. In April of the same year, Deng Xiaoping led the Chinese delegation to attend the sixth special session of the United Nations General Assembly, and made a speech at the conference on the 10th, expounding Chairman Mao Zedong's theory on the division of the three worlds, explaining China's foreign policy, and arousing widespread concern from all countries in the world. The strategic thinking of the three worlds points out that the Soviet Union and the United States are the first world, and they compete with each other for world hegemony. Third world countries and people, which account for the majority of the world population, are the main force in anti-imperialism, anti-colonialism and anti-hegemony. China, which accounts for one-fifth of the world's population, has changed from a semi-colonial and semi-feudal country to a powerful socialist country. Together with other socialist countries that insist on opposing imperialism and hegemony, China has firmly stood on the side of the third world and become an unshakable force in the third world. The developed countries between the above two, such as Britain, France, West Germany and Japan, are the second world. They have two sides and are the forces that the third world can strive for or unite in the struggle against hegemony. Chairman Mao Zedong's correct strategy of dividing the three worlds has provided a powerful ideological weapon for the international proletariat, socialist countries and oppressed nations to unite, establish the broadest United front, and oppose the Soviet and American hegemons and their war policies. The theory of the three worlds was an important basis for China to formulate foreign policy at that time.