The Glavnoe Razvedyvatelnoe Upravlenie served as the Soviet Union's chief military intelligence group, producing a network of spies that operated worldwide and still employs 100,000.
From the Zimmerman Telegram in 1917 through to recent breaking of Russian codes, many battles were won or lost because one side could read its opponent's intercepted messages.
Bletchley Park, an unassuming Victorian mansion 50 miles north of London, became the most potent deciphering center of WWII when its staff of code breakers cracked the Nazis' encrypting machine.
Lenin’s feared secret police, the Russian Bolshevik Cheka knew no bounds and was run by the dreaded Feliks Dzershinsky, who founded the Gulag Archipelago.
Take a look at the role played by intelligence-collection ships in all the major conflicts in the 20th century, from equipment transport to participation in international disputes.
Britain's counter-espionage service proved highly effective during both World Wars but later faced criticism for failing to expose the Cambridge spies.
The French had a sophisticated intelligence network, which was active during WWI, confronted the Bolsheviks during the inter-war years, and has continued from World War II to today.
Examine the story of Japans’ elaborate espionage network, including the build-up to Pearl Harbor and beyond.
One of the former Soviet Union's greatest espionage operations ended in 1951 when two young English diplomats at the British Foreign Office were revealed to have spent a decade funneling secrets to the KGB.
Learn about the history and reach of the Komitet Gosudarstvennoe Bezopasnosti (Committee for State Security), the agency of the former Soviet Union responsible for state security from 1954 to 1991.