Britain and France declare war on China (Second Opium War)

Political Context in London. Lord Palmerston, Prime Minister of the United Kingdom from 1855 to 1858, faced domestic opposition over the handling of the Arrow incident. On 3 March 1857, the British government lost a parliamentary vote regarding the Arrow incident and events at Canton. Palmerston attacked the patriotism of the Whigs who sponsored the resolution, and Parliament was dissolved. The censure motion was carried by a majority of sixteen, and the general election of April 1857 increased the government's majority.

Allied Military Preparations. Throughout 1857, British forces began assembling in Hong Kong, joined by a French contingent. The campaign faced logistical challenges when the Indian Mutiny became serious in May 1857, diverting troops originally destined for China. However, by December 1857, the coalition had sufficient ships and men to address the non-fulfilment of treaty obligations regarding entry into Canton. This buildup enabled the joint British and French army to attack and occupy Canton in late 1857.

Qing Dynasty Context. The Xianfeng Emperor, the eighth emperor of the Qing dynasty, reigned during the conflict. In 1856, an attempt to regain Nanjing was defeated and the Panthay Rebellion broke out in Yunnan. In China, the Second Opium War (1856–1860) was another humiliating defeat for a Qing dynasty already reeling as a result of the domestic Taiping Rebellion.