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What caused the First Opium War in 1839?

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Hong Kong: bridge — Guangdong Bridge between Hong Kong and Shenzhen, Guangdong province, on the Chinese mainland.

The First Opium War (1839–1842) was primarily caused by the Qing dynasty’s efforts to suppress the illegal opium trade, which had caused widespread addiction and severe economic and social disruption in China.123

For decades, British merchants had smuggled opium from India into China to correct a chronic trade imbalance, as there was high demand in Britain for Chinese tea, silk, and porcelain, but little demand for British goods. The resulting outflow of silver from China and the moral and physical toll of addiction prompted the Daoguang emperor to appoint Lin Zexu as imperial commissioner in 1839 to end the smuggling.4235

Upon arriving in Guangzhou, Lin confiscated and destroyed more than 20,000 chests of opium held by British merchants. This massive financial loss, combined with broader British dissatisfaction regarding the restrictive Canton system and the Chinese legal system, led to escalating tensions and the outbreak of armed conflict in late 1839.4236