Efforts to use espionage for military advantage are well documented throughout history. Sun Tzu, 4th century BC, a … 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 … 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 were at war. Armies grew much larger, with corresponding budgets. Likewise th… 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 was the Great Game, a period denoting th… See more

In Britain, the Secret Service Bureau was split into a foreign and counter-intelligence domestic service in 1910. The latter, headed by Sir Vernon Kell, originally aimed at calming public fears of large-scale German es… See more

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

Spying has sometimes been considered a gentlemanly pursuit, with recruiting focused on military officers, or at least on persons of the class from whom officers are recruited. However, the demand for male soldiers, an increase in … See more