Final answer:
In response to the Emperor of China's destruction of opium in Canton in 1839, the British launched military forces against China, resulting in the First Opium War, and ultimately imposed the Treaty of Nanjing in 1842 with severe consequences for China.
Step-by-step explanation:
In 1839, the Emperor of China ordered the destruction of opium stocks in Canton as a crackdown on the illegal opium trade. The British response was militaristic; they sent forces to China, marking the beginning of the First Opium War. The British military, utilizing their advanced technology and naval power, overwhelmed the Chinese defenses. Eventually, this led to the signing of the Treaty of Nanjing in 1842, which imposed heavy concessions on China, including ceding Hong Kong, opening various ports to European traders, and enforcing a large indemnity upon the Chinese government. Moreover, it stipulated that British citizens in China would be tried under British, not Chinese, law.