The major cause of Britain's war against China in the mid 19th century was mainly due to the forced opio exportation from Great Britain to China which generated a large number of addicts towards 1830, whereby the Emperor Daoguang decided to ban the opium's marketing and consumption in China. So, Britain was annoyed with that and decided to start a first war against China from 1839 to 1842, where China was defeated and had to accept the free comerce with Britain. And then, towards 1856 Britain asked to China to renegotiate the agreement signed in the Nanking Treaty of 1842, where they requested that they'll be allowed to free trade throughout the entire Chinese territory, that it'll be allowed the commercialization of opium legally, that it'll be ended the foreigners taxes, that it'll be eliminated the piracy and that it'll be normalized the transit of semi-slave employees, among other things, whereby China didn't accept and due to the China's disagreement and the incident of arrow in 1856, the British with French help began the second Opium war in 1857 until 1860 when China was defeated again and it was submitted the Tianjin's Treaty in 1858 and ratified in 1860.
