The First Opium War (1839-1842) was a crucial conflict between China and Britain, with the primary cause being the Chinese government's efforts to suppress the opium trade. The conflict ignited when Chinese officials confiscated and destroyed tons of British-imported opium. As a response, the British launched a military campaign to protect their economic interests and secure favorable trading rights in China.

One significant event during the war was the Battle of Chuenpi, where British forces successfully defeated the Chinese navy, gaining control of the Pearl River. This victory enabled the British to launch further attacks and advance towards the Chinese coast.

The war culminated in the signing of the Treaty of Nanking in 1842. Under the terms of this unequal treaty, China was forced to cede Hong Kong to Britain, pay a large indemnity, open up five treaty ports for British trade, and grant extraterritorial rights to British citizens. This treaty set a precedent for future treaties, known as the 'Unequal Treaties,' which significantly impacted China's sovereignty and led to increasing Western influence in the country's affairs.