The Open Door Policy is a concept in foreign affairs stating that, in principle, all nations shoul have equal commercial and industrial trade rights in China. 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.