Background to the Opium War
China exported large quantities of tea and silk to the West but purchased few goods in return. To balance their trade, European merchants began to bring opium to China during the early 1800's. The Chinese had outlawed the importation of opium, and so the Europeans were smuggling the drug.
Opium smuggling created much local disorder in China, and the large outflow of silver to pay for the opium seriously disturbed the economy. In March 1839, Chinese officials tried to stop the illegal trade by seizing 20,000 chests of opium from British merchants in Guangzhou. The Opium War then broke out between China and Britain. Britain easily won the war, which ended with the Treaty of Nanjing in 1842.
Excerpt adapted from the "China" article, The World Book Encyclopedia © 1999