"
Atomic spies" or "
atom spies" were people in the
United States,
Great Britain, and
Canada who are known 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 are still matters 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 it was firmly quashed by the U.S. government.