Allegations that the United States military used biological weapons in the Korean War (1950–53) were raised by the governments of People's Republic of China, the Soviet Union and North Korea in 1952. The story was covered by the worldwide press and led to a highly pubicised international investigation. US Secretary of State Dean Acheson and other US and allied government officials denounced the allegations as a hoax. For many years, the allegations continued to have a number of prominent supporters. In 1998, however, a large cache of Soviet, Chinese and North Korean documents were released indicating that the allegations were part of an elaborate disinformation campaign.