China had a long history of self-sufficiency and isolationism under successive dynasties, focusing on agriculture and manufacturing to support its large population. In the 18th century, the Qing dynasty was powerful but not interested in foreign trade or technology. The British began smuggling opium into China, leading to widespread addiction problems. When China demanded an end to the opium trade, Britain refused and defeated China in the Opium War of 1839-1842. As a result, China was forced to cede Hong Kong to Britain and open more ports to foreign trade and influence through unequal treaties, marking the decline of Chinese isolationism.