What caused the Opium war and what did England gain?

The Opium War (1839-1842) was primarily caused by China's efforts to suppress the opium trade, which was causing widespread addiction and social issues, while Britain sought to protect its lucrative opium exports from India to China. Tensions escalated when China confiscated and destroyed opium stocks, leading to military conflict. England emerged victorious, gaining the Treaty of Nanking, which ceded Hong Kong to Britain, opened several Chinese ports to British trade, and established a system of extraterritoriality for British citizens in China. This marked the beginning of significant Western influence and control in China.