The cultivation, use and trade of psychoactive and other drugs has occurred since the dawn of civilization. In the 20th century, the United States government led a major renewed surge in drug prohibition called the "War on Drugs." It was only in the 20th century that Britain and the United States outlawed cannabis. The British had gone to war with China in the 19th Century in what became known as the First and Second Opium Wars to protect their valuable trade in narcotics.