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In 1838 with the amount of smuggled opium entering China approaching 1,400 tons a year, the Chinese imposed a death penalty for opium smuggling and sent a Special Imperial Commissioner, Lin Zexu, to curb smuggling. This resulted in the First Opium War (1839–42). After the war Hong Kong island was ceded to Britain under the Treaty of Nanking and the Chinese market opened to the opium traders of Britain and other nations. The Jardines and Apcar and Company dominated the trade, although P&O also tried to take a share. A Second Opium War fought by Britain and France against China lasted from 1856 until 1860 and led to the Treaty of Tientsin, which legalised the importation of opium. Legalisation stimulated domestic Chinese opium production and increased the importation of opium from Turkey and Persia. This increased competition for the Chinese market led to India reducing its opium output and diversifying its exports.

Britian faught side by side with what country  in the second Opium war?
France