Spying, as well as other intelligence assessment, has existed since ancient history. In the 1980s scholars characterized foreign intelligence as "the missing dimension" of historical scholarship."Christopher Andrew and David Dilks, eds. The missing dimension: Governments and intelligence communities in the twentieth century (1984) Since then a largely popular and scholarly literature has emerged.Christopher R. Moran, "The pursuit of intelligence history: Methods, sources, and trajectories in the United Kingdom." Studies in Intelligence 55.2 (2011): 33–55. online Special attention has been paid to World War II,John Prados, "Of Spies and Stratagems." in Thomas W. Zeiler, ed., A Companion to World War II (2012) 1: 482–500. as well as the Cold War era (1947–1989) that was a favorite for novelists and filmmakers.Raymond L. Garthoff, "Foreign intelligence and the historiography of the Cold War." Journal of Cold War Studies 6.2 (2004): 21–56.
Early history
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 21st century for the Art of War. He advised, "One who knows the enemy and knows himself will not be endangered in a hundred engagements." He stressed the need to understand yourself and your enemy for military intelligence. He identified different spy roles. In modern terms, they included the secret informant or agent in place, (who provides copies of enemy secrets), the penetration agent (who has access to the enemy's commanders), and the disinformation agent (who feeds a mix of true and false details to point the enemy in the wrong direction to confuse the enemy). He considered the need for systematic organization and noted the roles of counterintelligence, double agents (recruited from the ranks of enemy spies), and psychological warfare. Sun Tzu continued to influence Chinese espionage theory in the 21st century with its emphasis on using the information to design active subversion.Philip H. J. Davies and Kristian C. Gustafson. eds. Intelligence Elsewhere: Spies and Espionage Outside the Anglosphere (2013) p. 45
Chanakya (also called Kautilya) wrote his Arthashastra in India in the 4th century BC. It was a 'Textbook of Statecraft and Political Economy' that provides a detailed account of intelligence collection, processing, consumption, and covert operations, as indispensable means for maintaining and expanding the security and power of the state.Dany Shoham and Michael Liebig. "The intelligence dimension of Kautilyan statecraft and its implications for the present." Journal of Intelligence History 15.2 (2016): 119–138.
Ancient Egypt had a intelligence gathering system. The Hebrews used spies as well, as in the story of Rahab. In the Bible (Joshua 2:1–24), The Ancient Hebrews sent spies to Jericho before attacking the city, one of the earlier sophisticated intelligence operations.
Spies were also prevalent in the Greek and Roman empires."Espionage in Ancient Rome". HistoryNet. Kataskopes graphe (κατασκοπῆς γραφή) was a legal action in ancient Athens specifically targeting spies. If a foreigner was caught engaging in espionage, they could be prosecuted under this action. The accused spy was often subjected to torture, typically by being placed on the rack, to extract information. Following this, they were typically executed. Athenian citizens who were guilty of espionage were prosecuted for prodosia (προδοσία, meaning treason), a different charge under Athenian law.A Dictionary of Greek and Roman Antiquities (1890), Kataskopes Graphe Trials for prodosia were typically conducted before the Athenian assembly, and the punishments for those found guilty were severe. The standard penalties included execution, the loss of the right to be buried in Attic soil (a significant dishonor), and the confiscation of the individual's property. In some cases, lesser forms of prodosia or related offenses may have been recognized and punished with fines.Harry Thurston Peck, Harpers Dictionary of Classical Antiquities (1898), Prodosia
During the 13th and 14th centuries, the Mongols relied heavily on espionage in their conquests in Asia and Europe. Feudal Japan often used shinobi to gather intelligence.
A significant milestone was the establishment of an effective intelligence service under King David IV of Georgia at the beginning of the 12th century or possibly even earlier. Called mstovaris, these organized spies performed crucial tasks, like uncovering feudal conspiracies, conducting counter-intelligence against enemy spies, and infiltrating key locations, e.g. castles, fortresses and palaces.
Aztecs used Pochtecas, people in charge of commerce, as spies and diplomats, and had diplomatic immunity. Along with the pochteca, before a battle or war, secret agents, quimitchin, were sent to spy amongst enemies usually wearing the local costume and speaking the local language, techniques similar to modern secret agents.
Early modern Europe Many modern espionage methods were established by Francis Walsingham in Elizabethan EnglandTobias P. Graf & Charlotte Backerra (2022) Case studies in early modern European intelligence, Journal of Intelligence History, 21:3, 237-250, DOI: 10.1080/16161262.2022.2141977.. His staff included the cryptographer Thomas Phelippes, who was an expert in deciphering letters and forgery, and Arthur Gregory, who was skilled at breaking and repairing seals without detection.Andrew, Secret World (2018) pp 158–90.Hutchinson, Robert (2007) Elizabeth's Spy Master: Francis Walsingham and the Secret War that Saved England. London: Weidenfeld & Nicolson. . pp. 84–121. The Catholic exiles fought back when the Welsh exile Hugh Owen created an intelligence service that tried to neutralize that of Walsingham.Anna Maria Orofino, "'Coelum non animum mutant qui trans mare currunt': David Stradling (1537–c. 1595) and His Circle of Welsh Catholic Exiles in Continental Europe." British Catholic History 32.2 (2014): 139–158.
In 1585, Mary, Queen of Scots was placed in the custody of Sir Amias Paulet, who was instructed to open and read all of Mary's clandestine correspondence. In a successful attempt to expose her, Walsingham arranged a single exception: a covert means for Mary's letters to be smuggled in and out of Chartley in a beer keg. Mary was misled into thinking these secret letters were secure, while in reality they were deciphered and read by Walsingham's agents. He succeeded in intercepting letters that indicated a conspiracy to displace Elizabeth I with Mary. In foreign intelligence, Walsingham's extensive network of "intelligencers", who passed on general news as well as secrets, spanned Europe and the Mediterranean. While foreign intelligence was a normal part of the principal secretary's activities, Walsingham brought to it flair and ambition, and large sums of his own money. He cast his net more widely than anyone had attempted before, exploiting links across the continent as well as in Constantinople and Algiers, and building and inserting contacts among Catholic exiles.Stephen Budiansky, Her Majesty's spymaster : Elizabeth I, Sir Francis Walsingham, and the birth of modern espionage (2005) online free to borrow
18th century The 18th century saw a dramatic expansion of espionage activities.Christopher Andrew, The Secret World: A History of Intelligence (2018), pp 242–91. 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 the foreign ministries all grew in size and complexity. National budgets expanded to pay for these expansions, and room was found for intelligence departments with full-time staffs, and well-paid spies and agents. The militaries themselves became more bureaucratised, and sent out military attaches. They were very bright, personable middle-ranking officers stationed in embassies abroad. In each capital, the attached diplomats evaluated the strength, capabilities, and war plans of the armies and navies.Jeremy Black, British Diplomats and Diplomacy, 1688–1800 (2001) pp 143–45. online
France The Kingdom of France under King Louis XIV (1643–1715) was the largest, richest, and most powerful nation. It had many enemies and a few friends, and tried to keep track of them all through a well organized intelligence system based in major cities all over Europe. France and England pioneered the cabinet noir whereby foreign correspondence was opened and deciphered, then forwarded to the recipient. France's chief ministers, especially Cardinal Mazarin (1642–1661) did not invent the new methods; they combined the best practices from other states, and supported it at the highest political and financial levels.William J. Roosen, "The functioning of ambassadors under Louis XIV." French Historical Studies 6.3 (1970): 311–332. online
To critics of authoritarian governments, it appeared that spies were everywhere. Parisian dissidents of the 18th century thought that they were surrounded by as many as perhaps 30,000 police spies. However, the police records indicate a maximum of 300 paid informers. The myth was deliberately designed to inspire fear and hypercaution; the police wanted people to think that they were under close watch. The critics also seemed to like the myth, for it gave them a sense of importance and an aura of mystery. Ordinary Parisians felt more secure believing that the police were actively dealing with troublemakers.Alan Williams, "Domestic Espionage and the Myth of Police Omniscience in Eighteenth-Century Paris" Consortium on Revolutionary Europe 1750–1850: Proceedings (1979), Vol. 8, pp 253–260.
British To deal with the almost continuous wars with France, London set up an elaborate system to gather intelligence on France and other powers. Since the British had deciphered the code system of most states, it relied heavily on intercepted mail and dispatches. A few agents in the postal system could intercept likely correspondence and have it copied and forwarded to the intended receiver, as well as to London. Active spies were also used, especially to estimate military and naval strength and activities. Once the information was in hand, analysts tried to interpret diplomatic policies and intentions of states. Of special concern in the first half of the century were the activities of Jacobites, English supporters of the House of Stuart who had French support in plotting to overthrow the Hanoverian dynasty in England. It was a high priority to find men in England and Scotland who had secret Jacobite sympathies.Jeremy Black, "British intelligence and the mid‐eighteenth‐century crisis." Intelligence and National Security 2#2 (1987): 209–229.
One highly successful operation took place in the Russian Empire under the supervision of minister Charles Whitworth (1704 to 1712). He closely observed public events and noted the changing power status of key leaders. He cultivated influential and knowledgeable persons at the royal court, and befriended foreigners in Russia's service, and in turn they provided insights into high-level Russian planning and personalities, which he summarized and sent in code to London.T. L. Labutina, "Britanskii Diplomat I Razvedchik Charl'z Uitvort Pri Dvore Petra I." ["British diplomat and spy Charles Whitworth at the court of Peter I"] Voprosy Istorii (2010), Issue 11, p 124-135, in Russian.
Industrial espionage