The Open Door Policy is a concept in foreign affairs. As a theory, the Open Door Policy originates with British commercial practice, as was reflected in treaties concluded with Qing Dynasty China after the First Opium War (1839-1842). Although the Open Door is generally associated with China, it was recognized at the Berlin Conference of 1885, which declared that no power could levy preferential duties in the Congo basin.
As a specific policy with regard to China, it was first advanced by the United States in the Open Door Notes of September-November 1899. In 1898, the United States had become an East Asian power through the acquisition of the Philippine Islands, and when the partition of China by the European powers and Japan seemed imminent, the United States felt its commercial interests in China threatened. U.S. Secretary of State John Hay sent notes to the major powers (France, Germany, the United Kingdom, Italy, Japan, and Russia), asking them to declare formally that they would uphold Chinese territorial and administrative integrity and would not interfere with the free use of the treaty ports within their spheres of influence in China.
In reply, each nation evaded Hay's request, taking the position that it could not commit itself until the other nations had complied. During this period there was a strong economic tension. However, by July 1900, Hay announced that each of the powers had granted consent in principle. Although treaties made after 1900 refer to the Open Door Policy, competition among the various powers for special concessions within China for railroad rights, mining rights, loans, foreign trade ports, and so forth, continued unabated.
The increasing disregard of the Open Door Policy was a main reason for the convocation of the Washington Conference (1921-1922) in Washington, D.C. As a result of the conference, the Nine-Power Treaty, again affirming the integrity and independence of China via the Open Door principle, was signed by the United States, Great Britain, Japan, France, and China. However, the Nine Power Treaty lacked any enforcement regulations.
With the Japanese seizure (1931) of Manchuria and the creation of Manchukuo, however, the Open Door principle formally ceased to exist.
The Open Door Policy has been an important policy that has led to an increase of trade, economic co-operation and interdependence between countries. The theory of the Open Door Policy is a cornerstone of the idea that trade is a natural right and although sovereign countries can counter such policies with isolationist attitudes, that would be legitimate the act would be unnatural for trade and communication with others is a natural right as cited in John Locke's famous treatises.