This article explores the reasons behind Japan's decision to give up its control over Taiwan in 1945. Japan's annexation of Taiwan was motivated by its desire for territorial expansion and resources, but during its occupation, the relationship between the two countries was complex. World War II was a turning point, and the Cairo Declaration and Potsdam Declaration demanded that Japan surrender all territories it had taken by force during the war, including Taiwan. China played an important role in Japan's surrender of Taiwan, and the United States also played a significant role in negotiating the terms of surrender. The impact of Japan's surrender on Taiwan was profound, with challenges faced in integrating it into China's political and economic systems.