During the twentieth century a series of international treaties or agreements were adopted with the aim of implementing a worldwide system for the control of drug abuse. Drug use and abuse at the beginning of the twentieth century was mainly seen as a local phenomenon in such countries as China, Myanmar (Burma), Persia, India, Egypt, Morocco, or among tribes in South America. Only the export of opium from Asian countries—or morphine, heroin, and cocaine from European countries to China—was seen as part of an international problem. China, which was a major consumer of drugs, was unable to deal with the problem on its own until agreements between China and Britain limited the export of opium from British India to China. Other sources of opium, however, replaced British India, and, when it became clear that bilateral agreements between countries were insufficient to prevent the traffic in drugs, the first international conference on narcotic drugs was held in Shanghai in 1909. This led to the adoption in 1912 of the International Opium Convention. It was soon realized that reporting and monitoring would be a necessary aspect of any drug control activity, and in 1925 a compulsory reporting system was created and a Permanent Central Board was established to monitor and supervise the compliance of governments that had entered into treaty obligations. Despite endless political and other confrontations between countries and governments, drug control measures were often excepted. For example, during the Cold War the two sides cooperated to develop and adopt the Single Convention on Narcotic Drugs of 1961, the Convention on Psychotropic Substances of 1971, and the United Nations Convention against Illicit Traffic in Narcotic Drugs and Psychotropic Substances of 1988.