Second Opium War: France and the United Kingdom declare war on China.

The Second Opium War, also known as the Second Anglo-Chinese War or Arrow War, was fought between the United Kingdom and France against the Qing dynasty of China between 1856 and 1860. It was the second major conflict in the Opium Wars, which were fought over the right to import opium to China, and resulted in a second defeat for the Qing and the forced legalisation of the opium trade. It caused many Chinese officials to believe that conflicts with the Western powers were no longer traditional wars, but part of a looming national crisis.