The Second Opium War was a major conflict between China and Western powers, primarily France and the United Kingdom. Tensions had been escalating due to the British opium trade, which China sought to suppress, leading to the First Opium War (1839-1842). After a series of events, including the seizure of the Arrow, a British-registered ship, by Chinese authorities, relations deteriorated further. In early 1857, the British government sought to reinforce its position in China, leading to a concerted response from both British and French forces. The draft of war was solidified as they sought leverage over trade agreements and the influence over Chinese policy. United in their interests, France and the UK formed a coalition to pursue military action against the Qing Dynasty, demanding greater trade rights and security for their nationals in China.

In subsequent military campaigns, the Allied forces met with fierce resistance, but they also employed superior military tactics and technology, leading to their eventual successes. The war would ultimately result in a series of treaties that forced China to accept unfavorable terms, including opening more ports to foreign trade and ceding territory, highlighted by the Treaty of Tientsin in 1856 and the Treaty of Peking in 1860. The declaration of war was not only a pivotal moment in this ongoing conflict, but it also reflected the broader imperialist ambitions of European nations in the 19th century as they sought to exert control over large parts of Asia, driven by economic interests in trade and commerce.