This Is the War That Destroyed China (And Could Be the Reason for Another Big War)
When the Qing sued for peace in 1842, the British could set their own terms. The Treaty of Nanjing stipulated that Hong Kong would become a British territory, and that China would be forced to establish five treaty ports in which British traders could trade anything they wanted with anybody they wanted to. A later treaty forced the Chinese to formally recognize the British as equals and grant their traders favored status.
In 1839, England went to war with China because it was upset that Chinese officials had shut down its drug trafficking racket and confiscated its dope.