Spying, as well as other intelligence assessment, has existed since ancient history. In the 1980s scholars characterized foreign intelligence as "the missing dimension" … See more

The 18th century saw a dramatic expansion of espionage activities. It was a time of war: in nine years out of 10, two or more major powers … See more

Modern tactics of espionage and dedicated government intelligence agencies were developed over the course of the late 19th … See more

• Reign of Elizabeth I of England
• English Commonwealth
• American Revolution See more

Efforts to use espionage for military advantage are well documented throughout history. Sun Tzu, 4th century BC, a theorist in … See more

Many modern espionage methods were established by Francis Walsingham in Elizabethan England. His staff included the cryptographer Thomas Phelippes, who was an expert in deciphering letters and forgery, and Arthur Gregory, who was skilled at breaking … See more

Civil intelligence agencies
In Britain, the Secret Service Bureau was split into a foreign and counter-intelligence domestic service in 1910. The latter, headed by Sir See more