Opium had been introduced into China in the 7th century. By the early 18th century opium addiction had become such a severe problem that the government tried to prohibit trade in it. The prohibition was a failure. When the British discovered the value of the opium trade in 1773, they determined to benefit. The Chinese paid the British for the opium, and the British in turn used the money as part payment for goods bought from the Chinese.

In 1839 the Chinese government made a concerted effort to suppress the opium trade. All the opium warehouses in Canton were confiscated. This serious effort, followed by a minor military incident, led to hostilities. In February 1840 the British sent an expedition against Canton.

The conflict, in which the more powerful British were victorious, was ended by the Treaty of Nanjing, which was signed on Aug. 29, 1842, and a supplemental treaty of Oct. 8, 1843. These treaties provided for payment of an indemnity of 21 million dollars by the Chinese, cession of five ports for British trade and residence, and the right of British citizens in China to be tried in British courts. It was at this time that Britain gained control of Hong Kong.

In October 1856 the Canton police boarded a British-registered ship, the Arrow, and charged its crew with smuggling. This incident led to the second war. In this war the British were joined by the French, and an Anglo-French force occupied Canton late in 1857. The Treaty of Tianjin in 1858 temporarily halted the fighting, opened new trading ports, allowed residence in Peking for foreign emissaries, gave freedom of movement to Christian missionaries, and permitted travel in the interior.

The Chinese refusal to ratify the treaty led to an Anglo-French attack on Peking and the burning of the Summer Palace. In 1860 the Chinese signed the Convention of Peking by which they promised to observe the 1858 treaty.