"Atomic spies" or "Atom spies" were people in the United States, Great Britain, and Canada who are thought to have illicitly given information about nuclear weapons production or design to the Soviet Union during World War II and the early Cold War. Exactly what was given, and whether everyone on the list gave it, is still a matter of some scholarly dispute, and in some cases what were originally seen as strong testimonies or confessions were admitted as fabricated in later years. Their work constitutes the most publicly well-known and well-documented case of nuclear espionage in the history of nuclear weapons. There was a movement among nuclear scientists to share the information with the world scientific community, but that was firmly quashed by the U.S. government.