The Second Opium War (simplified Chinese: 第二次鸦片战争; traditional Chinese: 第二次鴉片戰爭), 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.
On 8 October 1856, Qing officials seized the Arrow, a British-registered cargo ship, and arrested its Chinese sailors.