By the early 1800s, there were 10-12 million opium addicts in China. Although a ban was enforced on the drug in 1796, various social classes were affected. (Ames)
The Opium war started because China (Qing Dynasty) refused drugs from the British and thousands of civilians fell into addiction. (Ames)
China started accepting foreign trade in the 17th century in the port of Canton. Because the materials exported from Britain were declining, the British-owned East India Company (EIC) began importing opium to China.
The Opium Wars opened China to Western trade and influence but greatly reduced the Qing dynasty’s power and prestige, because of that the dynasty would last only about another 50 until it was overthrown in 1911/12.
According to 1847 British government report, it was shown that the casualties from Britain involved around 451 wounded and 69 killed. However, it is predicted for China to have 18,000 to 20,000 people killed or injured. (Encyclopædia Britannica)