By the late 18th century, the British East India Company (EIC) expanded the cultivation of opium in the Bengal Presidency, selling it to private merchants who transported it to China and covertly sold it on to Chinese smugglers.

Successive Chinese emperors issued edicts making opium illegal in 1729, 1799, 1814, and 1831, but imports grew as smugglers and colluding officials in China sought profit.

[14][page needed] Charles Elliot, Chief Superintendent of British Trade in China, arrived 3 days after the expiry of Lin's deadline, as Chinese troops enforced a shutdown and blockade of the factories.

The standoff ended after Elliot paid for all the opium on credit from the British government (despite lacking official authority to make the purchase) and handed the 20,000 chests (1,300 metric tons) over to Lin, who had them destroyed at Humen.

[13] After almost a year, the British government decided, in May 1840, to send a military expedition to impose reparations for the financial losses experienced by opium traders in Canton and to guarantee future security for the trade.

In the ensuing conflict, the Royal Navy used its superior ships and guns to inflict a series of decisive defeats on Chinese forces.

In spite of this, a new Imperial Commissioner, Ye Mingchen, was appointed at Canton, determined to stamp out the opium trade, which was still technically illegal.

Sir John Bowring, Governor of British Hong Kong, called up Rear Admiral Sir Michael Seymour's East Indies and China Station fleet, which, on 23 October, bombarded and captured the Pearl River forts on the approach to Canton and proceeded to bombard Canton itself, but had insufficient forces to take and hold the city.

On 15 December, during a riot in Canton, European commercial properties were set on fire and Bowring appealed for military intervention.

[22] The war resulted in the 1858 Treaty of Tientsin (Tianjin), in which the Chinese government agreed to pay war reparations for the expenses of the recent conflict, open a second group of ten ports to European commerce, legalize the opium trade, and grant foreign traders and missionaries rights to travel within China.

[18] China was also required to use diplomacy in the Western, egalitarian style instead of their normal way of conducting business with lesser states through a tribute system.

The fire burned for three days and nights, razing the buildings of the Old Summer Palace to the ground and destroying nearby royal properties.