China as a country with a highly developed manufacturing industry had no need for imported cotton fabrics or similar items produced in the West. The British merchants - especially the East India Company - saw their chance in the import of opium. As the import of opium had been prohibited by the Chinese government already during the 18th century, the only way to make profit by selling Indian opium was the smuggling business.

During the 1830s, the British merchants systematically built up their opium import system and thereby met the huge demand of Chinese opium consumers and addicted people. Opium does not only mean a danger for health, but also has a deep impact on public moral. Moreover, the export of tea, silk and chinaware was not able to cover the costs for opium imports: the Chinese trade balance tended to become negative, the silver money left the country and depreciated the copper coins - a fatal development for the lower classes of population as well as for the rich merchants of the Yangtse area. The court in Beijing was divided between ministers proposing a forced barter (opium against Chinese products); allowance of opium import but imposing high taxes on the drug; or confrontation with the British merchants.

A representative of the last group was Lin Zexu(林则徐) who acted as commissioner in Guangzhou (Canton) in 1839, the main import harbour of the south. He confiscated opium cases and tried to banish British merchants. But under the protection of their government, the Britains under Captain Elliott attacked some small harbors, occupied islands and threatened the port of Tianjin with canon boats: the begin of the so-called Opium War (Yapian Zhanzheng 鸦片战争). A British fleet, commanded by Henry Pottinger, proceeded until Nanjing, when the Chinese government finally gave in and signed the Nanjing Treaty (Nanjing Tiaoyue 南京条约) in 1842, the first of a long line of shameful treaties for the Qing government, called "unequal treaties" (bu pingdeng tiaoyue 不平等条约). For twenty centuries, Chinese emperors had dealt in the same way with penetrating "barbarians": making concessions to them by granting them material presents like Chinese silk or sending them princesses. In 1842, nobody in China was aware that the danger coming from the West was much deeper than a few nomad barbarians attacking the Chinese frontiers.

In the Nanjing Treaty, the Qing government granted the British free (opium) trade in the harbors of Xiamen (Amoy), Shanghai, Ningbo, Fuzhou and Guangzhou, abolishing the monopol of the Chinese merchant guilds in these cities. British goods were imposed with a very low import tax, and British subjects were allowed to move freely inside China.

As a trade base (shangpu 商埠), the island of HongKong (Xianggang 香港) was handed over to Great Britain. The financial damages China had to pay for the war counted 21 million silver dollars. Great Britain was officially recognized by the Qing government as a foreign power with equal rights. In an additional treaty, the Humen Treaty (Humen Tiaoyue 虎门条约), Great Britain was allowed to establish concessional settlement territories (zujie 租界) where British subjects were exempt of Chinese jurisdiction.

But the most important item of this treaty was the Most Favorite Clausula (Zuihuiguo Daiyu Tiao 最惠国待遇), allowing Great Britain to obtain every contractual concession any other country should obtain. Following the British, France (Treaty of Whampoa or Huangpu 1844 黄埔), the USA (Treaty of Wangsha 望厦条约), and the minor European states forced treaties with the Chinese allowing them free trade inside a handfull of harbor cities. France obtained the permission to dispatch missionaries to China.

Still unsatisfied with the Najing Treaty, the British merchants claimed residential rights in China. When the Chinese police confiscated a Chinese ship under British flag named Arrow in 1856, and at the same time a French missionary was killed, British and French saw their chance to revise the Nanjing Treaty. Unifying their armies (Ying Fa Lianjun 英法联军), British and French occupied Guangzhou and forced the Qing government to sign the Tianjin Treaty (Tientsin Treaty; Tianjin Tiaoyue 天津条约) in 1858 after their canon boats had bombarded the Dagu Forts 大古 near Tianjin.

But the French army invaded Beijing and burned down and plundered the Qing emperors' summer residence in the Yuanmingyuan Garden 圆明园; the court had fled to Jehol (Rehe 热河) in Manchuria. These military actions are called the Second Opium War. Signed in 1860, the Beijing Treaty (Beijing Tiaoyue 北京条约) allowed British and French subjects free trade, travel and mission in all places of China, basing on a couple of open harbors.

Damages of 16 million silver bars (tael) were added by the cession of the Kowloon Peninsula (Jiulong Bandao 九龙半岛) opposite to Hong Kong to Great Britain. British and French were subject only to their own jurisdiction, and the two countries were diplomatically recognized by the Qing government and the first real foreign ministry (Zongli Yamen 总理衙门).

Until then, China had seen all other countries as subject to the Qing empire. Additionally, many foreign goods were freed from import tax. The maritime customs office was confiscated and run by the British official Robert Hart to ensure the payment of damages China had to hand over to the Western Nations. China had lost her sovereignity over the import taxes, a field that normally provided the state treasury with a large income.

Meanwhile, Russia also claimed rights on Chinese territory. The treaties of Nerchinsk (chin. Nibuchu 尼布楚) in 1689 and Kyakhta (chin. Qiaketu 恰克土 or 恰克图) in 1727 already had regulated frontier line and trade between Qing China and Russia. In 1858 Russia occupied the territory north of the River Amur and clamied this territory as Russian, ensured in the Aigun Treaty (Aihui Tiaoyue 瑷珲条约).