The First Opium War and the Treaty of Nanjing
Britain fights a war to protect its opium trade and forces China to cede Hong Kong
Quick facts
- Treaty signed
- 29 August 1842, aboard HMS Cornwallis
- Territory ceded
- Hong Kong Island
- Treaty ports opened
- Shanghai, Canton, Ningbo, Fuzhou, Xiamen
What happened
British merchants had built a lucrative trade smuggling opium grown in India into China, reversing Britain's trade deficit and creating mass addiction that Chinese authorities tried to suppress by destroying opium stockpiles at Canton in 1839. Britain responded with a war fought largely at sea, where its modern steam-powered navy overwhelmed Qing forces. Negotiations were held aboard the British warship HMS Cornwallis, anchored in the Yangtze, and the Treaty of Nanjing was signed on 29 August 1842. China ceded Hong Kong Island to Britain, opened five treaty ports including Shanghai and Canton to Western trade, and agreed to pay a substantial indemnity for the destroyed opium.
Why it matters
Nanjing was the first of the so-called Unequal Treaties that Western powers imposed on a weakened China over the following decades, and it began what Chinese historians call the century of humiliation. Hong Kong Island remained a British colony until 1997.
How we know
The U.S. Department of State's Office of the Historian and the UK National Archives both document the treaty's terms and the war's diplomatic aftermath from official records of the period.
Sources
- U.S. Department of State, Office of the Historian. The Opening to China Part I: the First Opium War, 1839-1844 · Reputable sourcehistory.state.gov · The domain "history.state.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- The National Archives (UK). Hong Kong and the Opium Wars · Reputable sourcenationalarchives.gov.uk · The domain "nationalarchives.gov.uk" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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Related timelines
- History of China → · The war that begins China's century of humiliation