Was the Opium War really about opium, or about something bigger?

Both: opium was the spark, but historians disagree about what was really at stake. The First Opium War was fought between the British Empire and Qing China between 1839 and 1842. The immediate issue was China's enforcement of its ban on the opium trade, by seizing opium stocks from mainly British merchants at Guangzhou and threatening death for future offenders.

The drug was the engine of a huge trade. Opium was Britain's single most profitable commodity trade of the 19th century, and by 1831 the annual opium traffic neared 20,000 chests, compared with about 4,000 a year from 1800 to 1818. In China it caused real harm: many people became addicted and suffered chills, nausea and cramps when they stopped. In 1839 the Daoguang Emperor rejected proposals to legalise and tax opium and sent Lin Zexu to Guangzhou, where British dealers were forced to hand over 1,420 tonnes of it.

Britain's government supported the merchants' demand for compensation and insisted on free trade and equal diplomatic recognition. At home it had critics: a motion from the anti-war faction, who denounced the ethics of the opium trade, failed in Parliament by only nine votes. So some historians, such as Glenn Melancon, argue that the issue was not opium but Britain's need to uphold its honour, reputation and commitment to global free trade.

The Qing lost, and in 1842 were forced to sign the Treaty of Nanking, the first of what the Chinese later called the unequal treaties. It granted an indemnity, extraterritoriality and five treaty ports, and ceded Hong Kong Island. Twentieth-century nationalists considered 1839 the start of a century of humiliation.