Efforts to use espionage for military advantage are well documented throughout history. Sun Tzu, 4th century BC, a theorist in ancient China who influenced Asian military thinking, still has an audience in the … See more

Modern tactics of espionage and dedicated government intelligence agencies were developed over the course of the late 19th century. A key background to this development … See more

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

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

Civil intelligence agencies
In Britain, the Secret Service Bureau was split into a foreign and counter-intelligence domestic service in … See more

Spying has sometimes been considered a gentlemanly pursuit, with recruiting focused on military officers, or at least on persons of the class … See more