- 1839–42: First Opium War: war being fought between Great Britain and China after the latter attempted to suppress the opium trade. Great Britain wins. The conflict is ended by the Treaty of Nanjing (see below).
- August 29, 1842: Treaty of Nanjing: the treaty between Great Britain and China that ends the First Opium War. Among its provisions, China has to increase the number of treaty ports where the British can trade and reside from one (Canton) to five. It also cedes the territory of Hong Kong to Great Britain. This treaty ushers in the era of unequal treaties to which China is forced to succumb.
- October 8, 1843: Treaty of the Bogue (Humen): a supplement to the Treaty of Nanjing that gives Great Britain any rights in China that might be granted to other foreign countries. This is known as most-favoured-nation status. It also gives British citizens in China extraterritorial rights.
- July 3, 1844: Treaty of Wangxia: a treaty between the United States and China. One of the many provisions of the agreement stipulated that the United States should have any rights in China that might be granted to other countries.
- October 24, 1844: Treaty of Whampoa: a treaty between France and China that mimics the benefits already granted to the United States and Great Britain, including the most-favored-nation status.
- 1856–60: Second Opium War: also known as the Arrow War or the Anglo-French War in China. This war is about Great Britain and France wanting to extend their trading rights in China. They use various incidents as an excuse to go to war and force the Chinese into granting concessions to accomplish that goal. For the British, it is the Chinese boarding of a British-registered ship, the Arrow, in October 1856. For the French, it is the murder of a French missionary in the interior of China in early 1856. Although the allied troops force the Chinese into negotiations in 1858 and secure several concessions (see Treaties of Tianjin, below), the Chinese later refuse to ratify the agreements, and the war continues until 1860.
- May 16, 1858: Treaty of Aigun: treaty between Russia and China that delineates spheres of control for the two countries in the Manchuria region and stipulates that only Russian and Chinese vessels will be permitted to navigate the Amur, Ussuri, and Sungari (Songhua) rivers. The treaty is not ratified by China.
- June 1858: Treaties of Tianjin: negotiations during the Second Opium War by which Great Britain and France secure concessions from China. The terms include allowing for the opening of more ports in China, foreign travel in the Chinese interior, residence for Western envoys in Beijing, and freedom of movement for Christian missionaries. Russian and U.S. diplomats are also granted the terms that Great Britain and France have secured. Later that year, further negotiations in Shanghai legalize the importation of opium. The treaties are not ratified by China.
- October–November 1860: Beijing Convention: agreement comprising three treaties China forms with Great Britain (October 24), with France (October 25), and with Russia (November 14). The Beijing Convention signals the end of the Second Opium War. China accepts the treaties previously negotiated with Great Britain and France at Tianjin, extends the same terms to other countries, and also cedes to the British the southern portion of the Kowloon Peninsula adjacent to Hong Kong. Russia attains what it had sought in the unratified Treaty of Aigun and is also given jurisdiction over the lands east of the Ussuri and the lands south of Lake Khanka, which includes the settlement of Vladivostok.
- September 13, 1876: Chefoo Convention: a treaty negotiated at Yantai (Chefoo) between China and Great Britain following the murder of a British explorer by Chinese nationals. The agreement results in more Chinese concessions and the opening of several new ports.
- 1883–85: Sino-French War: war between China and France over the Chinese protectorate of Vietnam primarily fought in 1884–85. It is preceded by a series of skirmishes in 1883 as well as clashes in prior years. The fighting results in a stalemate and is ended by an armistice on April 4, 1885. This is followed by the Treaty of Tianjin, signed on June 9, 1885 (not to be confused with the Treaties of Tianjin, previously signed by China with Great Britain and France in June 1858), which cedes Annam (now in Vietnam) to France.
- August 1, 1894–April 17, 1895: First Sino-Japanese War: war between China and Japan over supremacy in Korea that is ended by the Treaty of Shimonoseki. The war, in which China is defeated, marks the emergence of Japan as a major world power and demonstrates the weakness of the Chinese empire. It also encourages the Western powers to make further demands of the Chinese government.
- September 6, 1899: Open Door policy, part one: the first of two notes comprising the Open Door policy, presented in the form of a circular (diplomatic note) sent by U.S. Secretary of State John Hay to Great Britain, Germany, France, Italy, Japan, and Russia regarding actions in China. Hay’s circular declares that (1) each great power should maintain free access to a treaty port or to any other vested interest within its sphere, (2) only the Chinese government should collect taxes on trade, and (3) no great power having a sphere should be granted exemptions from paying harbor dues or railroad charges. The replies from the various countries are evasive, but Hay interprets them as acceptances. Although many of Hay’s declarations are already being followed as a result of various treaties made with China in the past, Hay’s missive makes them the basis of official United States policy regarding China from that point on.
- c. 1899: The Boxer Rebellion: the peasant uprising that attempts to drive all foreigners from China. It begins slowly and gathers steam by year’s end, with Chinese Christians and Western missionaries being openly attacked. By May 1900 the government is secretly supporting the fighters, known as Boxers, and foreign troops enter China, sent by countries to protect their citizens. The rebellion is most active in 1900.
- June 21, 1900: China’s Empress Cixi openly supports the Boxer Rebellion and declares war on foreign nations with diplomatic ties in China.
- July 3, 1900: Open Door policy, part two: the second of two notes comprising the Open Door policy issued by Hay. Given the number of foreign troops in China present to protect the citizens of their countries in the ongoing Boxer Rebellion, his circular stresses the importance of preserving China’s territorial and administrative integrity while finding a solution to the crisis. Hay does not ask for replies, but all the powers except Japan express agreement with the principles.
- September 7, 1901: The Boxer Rebellion officially ends with the signing of the Boxer Protocol, which, among its provisions, allows for foreign troops to be stationed in China.
- October 10, 1911: A revolution is launched. The Qing dynasty, the last of the imperial dynasties of China, is overthrown and replaced by a republican government in 1912. The Chinese empire, which had endured for more than 2,000 years, comes to an end.
- January 18, 1915: Japan issues its Twenty-one Demands to China for special privileges in China—and is granted most of them—violating the Open Door principles. China’s capitulation to Japan on the demands ramps up anti-Japanese sentiment in China.
- February 6, 1922: Nine-Power Treaty (or Pact): agreement signed by the United States, Great Britain, Japan, France, Italy, the Netherlands, Portugal, Belgium, and China. It serves to reaffirm the principles of the Open Door policy. Specifically, it affirms China’s sovereignty, independence, and territorial integrity and gives all nations the right to do business with it on equal terms.
- September 18, 1931: Mukden Incident: seizure of the Manchurian city of Mukden (now Shenyang, Liaoning province, China) by Japanese troops. It is followed by the Japanese invasion of all of Manchuria and the establishment of the Japanese-dominated state of Manchukuo (Manzhouguo) in the area. Manchukuo declares it will respect the Open Door policy. Japan continues to occupy Manchuria until 1945.
- 1937–45: Second Sino-Japanese War: conflict that breaks out when China mounts a full-scale resistance to the expansion of Japanese influence in its territory, which Japan began in 1931. The war remains undeclared until December 9, 1941, and for most of its duration takes place at the same time as World War II (1939–45).
- 1940–41: In response to the Second Sino-Japanese War and the growing threat from Japan’s actions, the United States adopts a rigid stance in favor of the Open Door policy. This includes escalating embargoes on exports of essential commodities to Japan, such as aviation gas, scrap metal, steel, and oil. The embargoes are one of the primary reasons that Japan goes to war with the United States in late 1941.
- August–September 1945: World War II ends, as does the Second Sino-Japanese War. Japan is defeated in both. Changes to the world order diminish the importance of the Open Door policy.
- 1945–49: Chinese Civil War: the Nationalists (Kuomintang) under Chiang Kai-shek and the Communists under Mao Zedong battling for control of China.
- October 1, 1949: Mao proclaims the establishment of the People’s Republic of China; by the end of the year, the communists have control over just about all of mainland China. The communist victory brings to an end all special privileges for foreigners, rendering the Open Door policy meaningless.