Sun Yat-sen trained in medicine but turned toward political reform and the overthrow of the Qing dynasty. He founded the Revive China Society in Honolulu in 1894 and helped plan an uprising in Guangzhou the following year. Its failure forced him into exile, beginning years of fundraising, travel, and revolutionary organization among overseas Chinese communities.

In 1905 Sun helped unite revolutionary groups in the Tongmenghui in Japan. His Three Principles joined nationalism, democracy, and the people's livelihood. Repeated attempted uprisings failed, but revolutionary networks expanded. Sun was abroad when the Wuchang Uprising began in October 1911. Returning after the movement had spread, he was elected provisional president and took office at Nanjing on January 1, 1912. He relinquished the presidency to Yuan Shikai in a negotiated effort to secure the emperor's abdication and national unity.

The new republic quickly disappointed Sun's hopes. Yuan concentrated power, suppressed opposition, and eventually attempted to restore monarchy. Sun supported resistance and continued reorganizing his political movement, which became the Kuomintang. Following Yuan's death, regional military leaders dominated much of China. Sun established rival governments in Guangzhou, claiming to defend the republic's constitutional foundations, but dependence on military allies limited his authority. Conflict with Chen Jiongming in 1922 demonstrated the fragility of his southern base and the difficulty of combining revolutionary leadership with effective state control.

In his final years Sun sought Soviet assistance and reorganized the Kuomintang along more centralized lines. Cooperation with Chinese Communists produced the First United Front, while the Whampoa Military Academy trained officers for a projected campaign of national reunification. His political program included a period of party tutelage before full constitutional democracy, an approach with lasting and disputed consequences. Traveling north to discuss China's future, he died in Beijing in 1925 before the Northern Expedition began. Both the Kuomintang and the Chinese Communist Party later claimed elements of his legacy. His career's significance lies in revolutionary organization, republican ideals, and an enduring language of national renewal, while his brief presidencies and unstable regional governments show the limits of his practical power.