The Art of War: How Military Intelligence Decides Conflicts

It is the side of warfare that never really gets talked about, and that is for a reason. In peacetime, intelligence work is vital to any national security apparatus, any escalating tension or frozen conflict, and any resistance movement or non-state actor trying to further their goals. But in wartime, the value of good intelligence goes through the roof. A few choice words from a cultivated source can save a thousand lives further afield, a stolen scroll or flash drive can reveal an enemy's best-kept secrets, and if an agent can get advance notice of what an enemy plans to do next, they can do a lot more than simply saving the day. They can win the war.

Key Takeaways

Strategic intelligence assesses broad national capabilities and war readiness, while tactical intelligence guides real-time decisions at the unit level on individual battlefronts.
Human intelligence remains irreplaceable because human sources can infiltrate locations cameras cannot reach, place data in context, and think critically in real time.
Sun Tzu identified advance knowledge as the decisive factor separating effective commanders from ineffective ones as early as the fourth century BCE.
Sir Francis Walsingham built Queen Elizabeth I's spy network from scratch, foiled multiple assassination and invasion plots, and his intelligence work was critical in defeating the Spanish Armada in 1588.
The British Double-Cross System during World War II was so successful that Britain controlled the entire German spy network inside the UK and used it to misdirect around D-Day.
Soviet double agent Kim Philby, a high-ranking MI6 officer, exposed countless details about MI6 and CIA operations throughout the Cold War.

Strategic and Tactical Intelligence: Two Intertwined Levels

Military intelligence is the war all around the war, an urgent effort that goes on behind enemy lines, far away from the battlefield, and at the highest levels of tactical and strategic leadership. It is a study not just of the enemy, but of allies, neutral players, and even one's own troops. It is quiet, critical work, the kind of work that decides whether a battle has been won or lost before it is even fought. Military intelligence is typically broken down into two distinct, but intertwined levels: strategic intelligence and tactical intelligence. Strategic intelligence is all about the big stuff: the state secrets of an adversary nation that would dictate, by example, what force they could use to launch an attack, or how their chain of command will function under the duress of a major war. It is big-picture, often assessing broad topics like how ready a force is to do battle, what technology they are believed to have on their side, or how much punishment their military, their political system, and their economy can take before they are pushed to think about surrender. It is strategic military intelligence that decides when wars are fought or avoided, how those wars are going to look, and how a military or its branches will learn, on a grand scale, about the changing conditions of battle and pivot to respond. Tactical military intelligence is a bit different; it is the small-scale stuff, the thing that will dictate what a leader in the field will do with their unit, guide the course of individual battles and skirmishes, and help low-level planners dictate how different components of a military force can work together in real time. Tactical intelligence is not surveying satellite imagery to try and figure out whether a hostile nation has a secret submarine fleet at its disposal; it is about finding the satellite image that shows one such submarine sneaking up behind one of your navy's ships, and getting on the phone with that ship as soon as possible. It is scouts on horseback mapping difficult terrain and setting up ambushes, or a lone traveler in the night wandering into town and asking the tavern-keep just how many guards occupy a nearby fort. It is the basic spywork that will happen thousands upon thousands of times during the course of a war, saving a few lives here, or turning the tide of a skirmish there, often without any hope of setting off a broader cascade to end a conflict.

The Decision-Making Imperative: Information as a Force Multiplier

The primary goal of military intelligence is to ensure that whoever is calling the shots has as much information as possible to inform the decisions they make. That rule holds true whether the decision-maker is a king, a president, a general or admiral, or Sergeant Joe leading a group of eight men through the jungle. Regardless of rank, regardless of historical period, regardless of ideology or the conflict in question, the general set of decision-making criteria will typically be the same: achieve whatever strategic or tactical objective has been established, while minimizing loss of troops, equipment, and other resources on one's own side, to the extent that it is possible to do so. It is a series of very difficult decisions, where even the best military intelligence cannot eliminate risk, but the more information a decision-maker has, and the more reliable that information is, the better they can make those critical decisions when it is time. And if a military can establish not just solid pieces of intelligence, but a solid intelligence apparatus, then it will often make the difference between total victory and catastrophic defeat. As for where that intelligence comes from, many aspects of that answer have changed with time, but one, arguably the most important of all, has stayed the same: human intelligence. Provided by spies, covert agents, non-military sources, corrupt officials, captured or turned enemies, and an incredibly diverse cast of assorted others, human intelligence is all about people: finding people in the know, figuring out what they know, and using that knowledge to aid in a war effort. No matter how good a military is at intercepting letters, tapping phone calls, or taking photos from orbit, there is nothing better than a reliable human source.

HUMINT, SIGINT, and the Full Spectrum of Intelligence Collection

A human source might not be able to relay the level of contextual detail that an image could, or recount the exact transcript of a phone call from memory, but they can do things that are far more valuable. They can place data in context, they can ask the right questions or be present in the right places, they can infiltrate to places that cameras or listening devices cannot reach, and they can respond to information by thinking critically in real time. A satellite might tell you the location of a warehouse that you think is an arms depot, and intercepted signals might tell you what the enemy says they have inside, but a human agent can sneak in and confirm that weapons are present, observe how it is guarded in real time, and extract secrets from the commander in charge, who thinks your spy is a nice guy he met over drinks. No matter how good technology might be, there are some forms of intelligence that only human sources can collect, and every person, no matter their rank, their allegiance, or the strength of their resolve, can become a source if military intelligence work is done just right. Beyond human intelligence, or HUMINT, it is signals intelligence, or SIGINT, that makes up a bulk of the information that intelligence organizations past and present spend their time collecting. Signals intelligence can be anything from communications intercepts — by letter, telephone, digital sources, or anything else — to electronics intelligence, to telemetry. Intelligence analysts can pore over data on electromagnetic emissions picked up from a hostile nation, to identify a weapons system or an electronic device, or they can use sensors to identify missile tests, bomb detonations, or other real-world disruptions taking place far away. In ancient times, a signals-intelligence operative might have spent their time unsealing scrolls, reading their contents, and resealing them to make them seem as if they were never opened. Today, an operative in a similar situation might spend their days worming around in a foreign dictator's personal email inbox, or reading enemy communiques that are supposed to be kept classified. Modern military intelligence can come from a range of other vectors, depending on what a given agency has at its disposal. Acoustic intelligence uses sound waves to track the movement of ships through the sea, and much more importantly, to track the locations of submarines across the oceans of the world. Image-based intelligence involves the analysis of photos and videos taken from satellites, high- or low-altitude aircraft, spy balloons, or photographers on the ground, all of whom can provide critical information on everything from military operations to defensive fortifications to new weaponry or a nation's military-industrial complex. Radiation-based intelligence can capture unintentional energy signatures to give away the presence or nature of electronic systems. Even simple theft can be tremendously valuable; after all, there is perhaps no better way to understand a given weapon, vehicle, or warplane than to take one and reverse-engineer it.

From Ad-Hoc Spiderwebs to Centralized Agencies

As for how individual nations structure their military intelligence agencies, that is an answer that has changed significantly throughout history. In times long gone, many kingdoms or empires would run military intelligence through formal, but largely ad-hoc spiderwebs of informants and agents, relying on word of mouth, ships, horses, and other means to relay intelligence despite delays of days, weeks, or even months. Others might be more centralized or more regimented, especially in larger nation-states. Often, spywork would overlap with sabotage, assassination, and other covert operations — a rule that still holds true in many nations today. In modern nations, military intelligence agencies are typically more centralized, with clear chains of command, an abundance of desk analysts, and reliable mechanisms to interface with military and civilian leaders at all levels. Modern military intelligence involves close attention to detail while sifting through data at high volumes, the work that will keep a hundred desk analysts content for years, just to pore over the amount of knowledge that can be gleaned from a few days of spy operations. But as monotonous, even boring, as modern military intelligence can be from some perspectives, one small discovery made behind a desk can save the lives of hundreds of troops out in the field — and in a thriving military intelligence outfit, those discoveries happen every day. A caveat is warranted when discussing the history of intelligence work: a large portion of the things one would like to know will be forever kept secret. Some of it, the more modern stuff, is sealed behind top-secret designations and digital vaults that are encrypted so thoroughly that a lifetime attempting to break through would not be enough. Countless secrets died with the spies and rulers who knew them, while others were never written down, or were lost throughout the course of history.

Ancient Greece, Rome, and the Chinese Empires: Intelligence in Antiquity

Ancient Greece was a fractious collection of city-states that the philosopher Plato considered to be in a permanent state of war with each other, be it declared or undeclared. Among the earliest discussions of wartime intelligence came from the writing of Aeneas Tacticus, who expressed a detailed understanding of what military intelligence would have been in his time: a combination of reconnaissance done by scouts on foot or on horseback, and espionage, where disguised or hidden spies collected information on their enemies, and found ways to get that information back to their own city-state. By accounts of the period, Greek spies were everywhere in each other's city-states, compromising each other's officials and playing protracted games of cat-and-mouse. Slaves would have been among the most valuable assets to cultivate; they were little-known, could enter and exit sensitive areas while hardly being noticed, and often had a deep and lasting animosity toward their captors that a foreign spy would gladly exploit. The Roman Empire, too, had an extensive intelligence network at its disposal, one that waxed, waned, and grew more efficient or more corrupt based on the political leadership of the time. Although Roman authors often told of their empire's disdain for subterfuge, and their strong preference for disciplined military units and strategic brilliance, the truth of the Empire was far less clear-cut. The use of agents to infiltrate hostile clans, make partnerships with non-Roman warlords, and rely on scouts and advance intelligence to guide the work of their legions, was a major element in Rome's ability to spread itself so far across the Mediterranean. During its conflicts with Carthage, the Carthaginian general Hannibal proved adept at spywork, with his agents able to infiltrate not just Roman camps but their capital city itself. Hannibal was personally known for his skill in disguise, and his agents were expert in forgery, secret communication, and feeding false or misleading information to Rome in order to orchestrate traps and ambushes. One such spy, who mistakenly led Hannibal's forces into a trap, was crucified as penalty. Across the Mediterranean at this time, rulers in the modern-day Middle East and North Africa were known for having formalized intelligence services at their disposal, whereas Rome's were far more ad-hoc. Far across Eurasia, the ancient empires of China had their own extensive history in military spycraft. From as early as the fourth century BCE, intelligence work was critical in guiding empires and warlords of the time into favorable military engagements, pre-empting attacks, and rooting out complex plans to bring about their downfall. In The Art of War, Sun Tzu emphasized the key role of intelligence work: "The means by which enlightened rulers and sagacious generals moved and conquered others, that their achievements surpassed the masses, was advance knowledge." In another volume, written by Sun Tzu's disciple Han Feizi, a spymaster of the time could study a full forty-seven signs of a failing state, illustrating pressure points and weaknesses from impetuous rulers to indecisive royal advisers to a neglected defense apparatus. Later volumes, from Military Methods to the Sima Fa to the Wu Zi and the Six Secret Teachings, all expounded on the nature of military intelligence and the many tactical and strategic errors that commanders of the time were making.

Medieval Espionage, the Shinobi, and Walsingham's Spy Network

Military intelligence was just as critical in the medieval period in Europe, where spies of that era had their own collections of tomes and philosophical volumes on espionage that they could rely on, if they knew where to look. Knowing the location of an enemy force and knowing its strength were particularly critical bits of knowledge in eras characterized by roving war parties and raider units rather than massive armies. In situations where a force that was ten men larger could easily overwhelm its enemy, the unit that had better scouts, could arrange ambushes, or could mislead their adversary could make up for a disadvantage or deliver a crushing defeat. As kingdoms gathered their strength, established bureaucracies, and amassed larger and better-equipped armies, so too did their intelligence networks stabilize and then centralize. In feudal Japan, there was perhaps no better expression of military intelligence than the shinobi — better known today as the ninja. Although spies or assassins would have been nothing new by the time the shinobi appeared, they were a much-needed institution in their era, the dark side of a system in which samurai codes dictated how and when military engagements took place. Left to exist by itself, a strict following of samurai doctrine would often lead to military ruin, and then societal devastation, but with the hidden hand of intelligence, assassination, guerrilla warfare, and sabotage at work behind the scenes, a cunning leader could better lay the groundwork for their warriors' success in open combat. Beginning in the twelfth century, shinobi were recruited as lowborn farmers and villagers, and trained in combat and espionage in secretive strongholds. Both men and women were welcome among their ranks, so long as they were willing to go to the lengths that the feudal lords, the daimyo, could not ask their own soldiers to go. Daimyo who relied on the shinobi and paid well were far more likely to find success in combat, making them a critical, if unsavory, influence in the centuries of war that preceded the peaceful Edo Period. In Europe, perhaps the most pivotal Renaissance-era figure of military intelligence was Sir Francis Walsingham, Spymaster General for Queen Elizabeth I. Walsingham served his Queen at a time of intense international intrigue, including several major wars and an overall environment where the outbreak of hostilities was always just a few short missteps away. He built a spy network for the Queen from the ground up during his time as Secretary of State, discovering a plot by Catholic nobles to overthrow Elizabeth I, and an unrelated plot to assassinate her. With threats only rising against the throne, Walsingham stepped fully into the role of spymaster, foiling a wide range of plots during his tenure and even discovering plans for a joint French and Spanish invasion of England. His intelligence work near the end of his life was critical in the defeat of an attacking Spanish armada in 1588. Walsingham's legacy can trace directly to Britain's modern military intelligence organizations, MI5 and MI6.

The Civil War, the Great Game, and the Telegraph Revolution

In the United States, the Civil War of 1861 to 1865 saw both the Union and Confederate militaries rely heavily on their intelligence branches, including spies on the ground, army and cavalry scouts, and newer advances like spy balloons and telegraph transmissions. Both sides of the conflict were heavily incentivized to rely on said telegraph technology, creating epicenters of intelligence where information could be processed, analyzed, and responded to in real time, across multiple battlefronts at once. In Europe, the telegraph and other methods of fast communication over long distances would lead to a similar rethinking of military intelligence, and around the world, these new technologies would prompt a turn toward centralization not long after they arrived. With that changing landscape came a greater emphasis on counterintelligence. Finding and eliminating enemy spies had always been important, but now those enemy spies could create catastrophe in a matter of minutes in the right circumstances, instead of having their messages delayed by days or even weeks before they could be delivered. With that speed came an exponential increase to the damage they could do, taking advantage of openings or sensitive moments that would, a few decades earlier, have been over far too quickly for an enemy to exploit. Across the world in Central Asia, Britain and Imperial Russia fought their own war of intelligence in the Great Game, a decades-long strategic rivalry in which both nations struggled to gain influence in Persia, Afghanistan, Tibet, and elsewhere. Overall, it resembled a 19th-century version of the Cold War, with military proxy conflicts, territorial grabs, and most of all, spywork dictating which side was being forced backward or being allowed to gain ground. Both sides started the conflict with their intelligence apparatus thrown together only haphazardly; by example, it was not uncommon to see British intelligence agents trying to pretend that they were archaeologists, without having any knowledge or equipment that one might expect to see from an actual archaeologist. But by the end of the conflict, both Britain and Russia had well-established, modernized intelligence networks, with separate bureaus for foreign and internal affairs, plus surveillance, cryptographic, and military-reconnaissance capabilities.

World Wars, Enigma, and the Double-Cross System

During World War I, intelligence services found themselves in the same predicament that just about every other element of every other global military did: they were woefully unprepared for the adversity they would face or the intensity of the conflict. Even leading up to the war itself, the decision of each individual nation to participate was born out of intelligence estimates that suggested they and their respective alliances could quite thoroughly outmatch the other, an assumption that was quickly proven wrong on all sides. To the extent that military intelligence existed at the start of the conflict, much of the thinking by high-level decision-makers was outdated at best, and quite naïve as to what modern military intelligence would or could be. The war witnessed the rise of large-scale covert action, with each side trying to sabotage each other, inflame internal tensions, and steal valuable secrets. Cryptography and aerial reconnaissance both evolved at stunning rates, while on the ground, the work of individual scouts became all the more important in trying to break a vast continental stalemate. If World War I was a war of rapid advancement in military intelligence, World War II would be the testing ground for every nation involved to elevate their understanding to the next level. On the intelligence side of World War II, codebreaking was key — most prominently in regard to the Enigma codes of Nazi Germany, but in reality, the battle to crack each nation's wide range of codes and ciphers was one of the most critical elements of the entire war. Overall, it was the Allies who came away with the victory, having cracked some of the most top-secret German, Japanese, and Italian codes over the course of the conflict, and it was the intelligence gleaned from those intercepts that allowed the Allies to turn the tide of the war. Also worthy of mention was the misdirection that took place in the counterintelligence sphere, most prominently in the British Double-Cross System. The operation was a protracted effort by the British to identify and turn German agents over the course of the war. It was so comprehensive and so resoundingly successful that by the latter years of World War II, Britain controlled the entire German spy network inside the UK. That control was then used to conduct immensely successful misdirections around the D-Day landings and the subsequent Allied push toward Berlin.

The Cold War, Modern Conflicts, and the Digital Future of Espionage

From World War II, the globe shifted focus into the Cold War, which, by all accounts, was a military intelligence era without parallel. Over decades of tensions between the Soviet Union and its allies on one side, and the global West on the other, espionage became not just the cornerstone of each side's long-term strategy, but a functional substitute for war itself. Each side picked up major victories and defeats during that time; for example, the Soviets were able to cultivate a high-ranking British MI6 agent named Kim Philby for years, turning him into an incredibly successful double agent who exposed countless details about the inner workings of MI6 and the CIA. On the Allied side, the CIA had more than its fair share of involvement in acts of global subterfuge, toppling governments, setting up intelligence networks, and enjoying new tools like the U-2, the SR-71, and eventually even military satellites to gather massive amounts of image and signals intelligence. The Cold War saw military espionage go through another wave of modernization, as advanced technology from telephones to radar to miniaturized radios and cameras significantly broadened the scope of what a spy could do. In the modern world, the utility of military intelligence is as great as ever. From American wars in Afghanistan and Iraq, to Chinese influence operations around the world, to Russian intelligence efforts in advance of invasions of Georgia and Ukraine, military intelligence is indispensable to the practice of modern warfare. As many countries around the world see their citizenry become less tolerant of military casualties and less open to the idea of wars abroad, military intelligence has become essential in dictating when and where the practice of open warfare is necessary, and streamlining it in order to maximize efficiency and minimize involvement overall. Modern military intelligence services are a hallmark of any nation that wishes to extend its influence beyond its own borders, from global superpowers like America and China, to rising international players like India, Israel, Brazil, and more. As intelligence work continues to evolve, signals intelligence and other digital measures of data-gathering have begun playing a larger and larger role, relative to the human intelligence that the nations of the world have relied on for so long. Between drone technology, advanced satellites, cyber-warfare capabilities, and other emerging methods of intelligence-gathering, the grand scope of military intelligence looks very different than it used to. Artificial intelligence tools are becoming all the more powerful, and the world's mightiest nations are not only establishing their own Space Forces but realizing that those new military branches have quite a bit of intelligence work to do. Yet under the surface, in every modern conflict, every new or developing Cold War, every geopolitical push and pull around the world, the battles waged in the intelligence world are the ones that precede, or prevent, the conflicts that are settled with bullets and blood.

Frequently Asked Questions

What is the difference between MI5 and MI6?

The Security Service, commonly known as MI5, is the United Kingdom's domestic counter-intelligence and security agency, focusing on protecting the UK from internal threats such as terrorism, while MI6 is responsible for foreign intelligence gathering, operating outside the UK to collect intelligence on other countries and organizations, with MI5's mission being to keep the country safe from domestic threats for over a century.

Is James Bond a MI5 or MI6?

James Bond is typically depicted as a member of MI6, the British foreign intelligence service, rather than MI5, which handles domestic counter-intelligence, reflecting the international nature of his espionage work and the focus of MI6 on gathering intelligence abroad.

What were the Punic Wars between Rome and Carthage?

The Punic Wars were a series of three wars fought between the Roman Republic and the Carthaginian Empire from 264 to 146 BC, with the First Punic War beginning before 264 BCE, as the two rival powers built up their territory and influence, ultimately leading to conflicts that would shape the Mediterranean world for centuries to come.

What was the main reason Rome fought Carthage in the Punic Wars?

The main reason Rome fought Carthage in the Punic Wars was due to the expansion of both powers and the competition for territory and influence in the Mediterranean, with control of the sea and trade routes being a significant factor, as both Rome and Carthage sought to establish dominance over the region from 264 to 146 BC.

How many wars were there between Rome and Carthage?

There were three Punic Wars fought between Rome and Carthage, spanning from 264 to 146 BC, with each war having distinct causes and outcomes that ultimately led to the rise of Rome as the dominant power in the Mediterranean.

Are MI5 spies real?

MI5, the Security Service, is a real organization with a mission to keep the UK safe from domestic threats, and while the specifics of their operations and the identities of their agents are not publicly disclosed, it is acknowledged that MI5 engages in intelligence gathering and counter-intelligence activities to protect national security, making the concept of MI5 spies real in the context of their work.

What are the 5 rules of The Art of War?

The Art of War, an ancient Chinese military treatise, does not explicitly outline five rules but rather provides principles and strategies for warfare, including the importance of knowing oneself and the enemy, choosing the right battlefield, and adapting to changing circumstances, with its timeless guidance on warfare tactics, intelligence gathering, and strategic thinking remaining relevant across centuries.

What are the 4 types of spies?

According to the principles outlined in The Art of War, there are indeed different types of spies or intelligence gatherers, but the text specifically mentions the importance of human intelligence provided by various sources, including spies, covert agents, and others, without explicitly categorizing them into four distinct types, emphasizing instead the value of reliable human sources in military intelligence.