The United Kingdom captures Hong Kong as a base as it prepares for the First Opium War with Qing China.

The First Opium War, also known as the Anglo-Chinese War, was a series of military engagements fought between the British Empire and the Chinese Qing dynasty between 1839 and 1842. The immediate issue was the Chinese enforcement of their ban on the opium trade by seizing private opium stocks from mainly British merchants at Guangzhou and threatening to impose the death penalty for future offenders. Despite the opium ban, the British government supported the merchants' demand for compensation for seized goods, and insisted on the principles of free trade and equal diplomatic recognition with China. Opium was Britain's single most profitable commodity trade of the 19th century. After months of tensions between the two states, the Royal Navy launched an expedition in June 1840, which ultimately defeated the Chinese using technologically superior ships and weapons by August 1842. The British then imposed the Treaty of Nanking, which forced China to increase foreign trade, give compensation, and cede Hong Kong Island to the British. Consequently, the opium trade continued in China. Twentieth-century nationalists considered 1839 the start of a century of humiliation, and many historians consider it the beginning of modern Chinese history.

The Qing dynasty, officially the Great Qing, was a Manchu-led imperial dynasty of China and an early modern empire in East Asia. Being the last imperial dynasty in Chinese history, the Qing dynasty was preceded by the Ming dynasty and succeeded by the Republic of China. At its height of power, the empire stretched from the Sea of Japan in the east to the Pamir Mountains in the west, and from the Mongolian Plateau in the north to the South China Sea in the south. Originally emerging from the Later Jin dynasty founded in 1616 and proclaimed in Shenyang in 1636, the dynasty seized control of the Ming capital Beijing and North China in 1644, traditionally considered the start of the dynasty's rule. The dynasty lasted until the Xinhai Revolution of October 1911 led to the abdication of the last emperor in February 1912. The multi-ethnic Qing dynasty assembled the territorial base for modern China. The Qing controlled the most territory of any dynasty in Chinese history, and in 1790 represented the fourth-largest empire in world history to that point. With over 426 million citizens in 1907, it was the most populous country in the world at the time.