Espionage is a term used for spies that go to other countries
They had many cool and hidden weapons
This was happening during the Cold War almost the whole time from 1947-1991
This was involved between the United States (CIA, NSA, FBI, and DIA) and the Soviet Union (KGB and GRU).
Klaus Fuchs was considered to be the best and most valuable spy
Klaus Fuchs was a German who spied for the Soviet Union and supplied information from the Americans, Britain, and Canadian manhatten project.
This all took place after WWII from the tension between the U.S. And the Soviet Union