French Indochina and the Cần Vương Resistance

France built its Southeast Asian empire step by step. French forces attacked Da Nang in 1858 and captured Saigon in 1859, citing the persecution of Catholic missionaries and seeking trade. In 1862 the Vietnamese Nguyễn court ceded three southern provinces, and France made Cambodia a protectorate in 1863. French expansion into northern Vietnam led to war with China, which claimed Vietnam as a tributary, in 1884–85, after which China recognized French control.

In 1887 France created the Indochinese Union, and it took Laos from Siam in 1893. Vietnamese resistance was strong: when the young emperor Hàm Nghi fled the capital at Huế in 1885, he issued a call known as Cần Vương, meaning 'aid the king,' and scholar-officials led guerrilla resistance until the 1890s. The French developed rice exports, rubber plantations and mines, while heavy taxes and state monopolies on salt, alcohol and opium burdened Vietnamese peasants.