People take it for granted that good intelligence wins wars. During most of Western history, however, warriors paid intelligence little heed, because it rarely helped them. Generals since Caesar have sought information about their enemies, of course, but for centuries they believed only what they could see: terrain and troops. They distrusted spies and questioned the tools of prediction -- dreams, omens, entrails, the mutterings of oracles. So inefficacious were these methods that of the "fifteen decisive battles of the world" described by the Victorian historian Edward Creasy, intelligence drove the outcome of only one: Rome's victory over Carthage at the Metaurus River in 207 BC. The rest were decided by strength and will.

But the situation changed in the nineteenth century as armies began to use railroads and developed general staffs for centralized planning, creating both a target for intelligence gathering and an organizational home for the information gathered. Even so, intelligence did not have a major impact on war and politics until communications intercepts in World War I helped generals to win battles -- a trend that continued in later conflicts.

Military intelligence thus progressed through three stages. In the nineteenth century, general staffs institutionalized it; during World War I, radio intercepts gave it importance; and during World War II and the Cold War, it played such a large role that intelligence officers gained equality in rank with combat commanders. The latter rightly retained priority, however, for intelligence in war works only through force. It can focus and economize efforts, it can offer an advantage, but in the end, force is necessary for victory. This remains true even of the war on terrorism, a shadowy campaign against nonstate actors in which intelligence is playing its greatest role yet.


Premodern military commanders made use of advisers, but they generally derided thinking and exalted fighting. Shakespeare summed up their attitude nicely in Troilus and Cressida, when he had Ulysses complain:

    They tax our policy and call it cowardice,
    Count wisdom as no member of the war,
    Forestall prescience and esteem no act
    But that of hand. The still and mental parts
    That do contrive how many hands shall strike
    When fitness calls them on, and know by measure
    Of their observant toil the enemy's weight,
    Why, this hath not a finger's dignity.
    They call this "bed-work," "mapp'ry," "closet-war."
    So that the ram that batters down the wall,
    For the great swinge and rudeness of his poise
    They place before his hand that made the engine,
    Or those that with the finesse of their souls
    By reason guide his execution.

In the seventeenth and eighteenth centuries, this attitude started to change with the emergence of army quartermasters, who were responsible for scouting terrain, planning marching routes and encampments, and furnishing supplies. French military historians trace the modern general staff to an 1801 pamphlet by the adjutant Paul Thiébault; their German counterparts, to an 1801 memorandum by Colonel Christian von Massenbach. Both documents mention intelligence. Thiébault proposed creating a general staff divided into four bureaus, one of which would deal with spies, guides, and prisoner exchanges. Massenbach, then a quartermaster, noted that officials "must know not only their own country, they must also know the neighboring states; they must not only be in the position to indicate those positions that we, under certain conditions, would have to take, but also those which the enemy commander, under these very conditions, would take, and would have to take."

The French Revolutionary Wars marked the advent of large armies of civilians. This led to the evolution of officer corps and, within them, permanent planning staffs. But neither those developments nor the arrival of railroads produced special units for evaluating intelligence. Only after a defeat had shamed a nation, or the prospect of one had stung it, did military establishments change their ways. If armies wanted to defend themselves against an attack, they had to know or believe that one was coming. They needed a staff unit to gather and weigh all kinds of intelligence. The role of defeat in spurring the establishment of such branches in Western armies is universal.


Russia was among the first countries to create a unit for intelligence evaluation, spurred by its capitulation in the Crimean War in 1856. The newly enthroned liberal tsar, Alexander II, had been impressed by Colonel Dmitri Miliutin, an instructor in the staff academy who had published a two-volume study of military statistics based on a sojourn in Prussia, and named him war minister in 1861. Miliutin set about modernizing the Russian military staff. By 1865, one of its six departments was devoted to gathering and evaluating information about foreign armies.

Following its defeat by Prussia in 1870­71 in the Franco-Prussian War, France hastily created a modern military general staff modeled after that of its enemy, which had developed one during the Napoleonic Wars. Improved and made permanent in 1874, the French general staff had six bureaus, including one dealing with what was at first called "military statistics" and later "intelligence." The sting of 1870­71 drove France, in a revanchist fervor, to become the leader in military code breaking by World War I.

Meanwhile, Austria had taken similar steps. Austria and Prussia had mobilized against each other in 1850 over the leadership of the Germanic Confederation, and although Prussia ultimately backed down, Austria had been scared. Immediately after demobilization, it combined its staff's intelligence-gathering and intelligence-evaluating elements into the Evidenzbüro. Then, in 1911, during the Tripolitanian War (both of whose combatants, Italy and the Ottoman Empire, bordered on Austria), Austria began to intercept and solve foreign military cryptograms, developing an expertise second only to France's.

The United Kingdom, for its part, had set up the Depot of Military Knowledge in 1803, with two of its four departments devoted to maps and a library, but it had degenerated due to a scandal and inactivity during the long peace in Europe. A retired engineer in the Indian army, Major Thomas Best Jervis, pressed for a topographical department in the Foreign Office but was rebuffed until he serendipitously obtained a Russian military map of the Crimea just after the outbreak of the Crimean War, in 1853. The British army then set up the Topographical and Statistical Department under his direction to provide copies of the map to British forces in the field. Later on, alarmed by Russia's resumed advance toward India in the 1860s, the opening of the French-owned Suez Canal in 1869, and the sudden appearance of victorious Prussians in Paris in 1870, the United Kingdom started to worry about defending itself and its empire. A reformist secretary of state for war, Edward Cardwell, formed an intelligence branch in 1873. It did not help much during the Boer War, however, as the British initially lost battle after battle. And so, after a postwar investigation, Parliament created a general staff, with intelligence as one of the four subdivisions of its Military Operations Directorate.

During the nineteenth century, the United States neglected intelligence just as it did the rest of its armed forces. Protected by the oceans, the Monroe Doctrine, and its vast military potential, the country felt little need for more security. But revelations about the army's embarrassing lack of planning for the Spanish-American War tarnished the reputation of the U.S. armed forces almost as much as a defeat would have. And so in 1903, Congress set up a general staff -- which included, for the first time in U.S. history, a permanent peacetime unit for intelligence evaluation modeled on France's.

And what of the military whose professionalism had inspired all the others? The chief of Prussia's Great General Staff had written in 1814 that "the work of the general staff in peacetime is to prepare everything for war; the most exact knowledge of the state and of neighboring states is its main duty." In fact, however, he and his successors saw intelligence not as a distinct function but rather as one of many inputs into planning. The Prussian staff's branches prepared for fighting in three areas -- the east (Russia), the west (France), and the rest (including Italy and the United Kingdom) -- by providing raw intelligence directly to the officers responsible for planning campaigns.

As war with Austria approached in 1866, Chief of the General Staff Helmuth von Moltke established an intelligence bureau to gather information about the enemy (it persisted as a spy agency through World War I). In 1867, Moltke set up another specialized agency, a geographic and statistical branch, to collect what would today be called "open-source intelligence" about other countries. The branch bounced from section to section of the general staff until it was abolished in 1894 and its functions distributed elsewhere. Prussia established a unit to evaluate all-source intelligence during the Franco-Prussian War but abolished it after the conflict ended. So the most successful general staff of all never set up a permanent peacetime agency for the evaluation of intelligence. Why not? Because in the century following the Napoleonic Wars, Prussia never suffered a major defeat.


Once formed, the intelligence-evaluation staffs of Western militaries dutifully monitored the foreign press and foreign government documents, analyzed railroad maps, and scrutinized spy reports. The officers who served in those staffs were not an army's best men. Military services believed that leading troops was more important than finding out what the enemy was doing, and so they put their brightest stars into battlefield command rather than intelligence. In addition, many officers shunned such a career because they felt that dealing with spies was dishonorable.

During this era, moreover, militaries were fixated on offense. The commanders of all the major European armies planned to start the next war with an attack, convinced that this was the quickest and surest path to victory. The United Kingdom's Field Service Regulations of 1909 expressed the view succinctly: "Decisive success in battle can be gained only by a vigorous offensive." And since the offense seeks to impose its will on the enemy, and is, as Clausewitz said, "complete in itself," it does not require knowing much about that enemy. Thus, even though intelligence evaluation now had a home, it was not a respected one.

The situation changed in World War I, which differed from previous wars in its intensive employment of modern technology. For intelligence, the greatest impact came from radio. Much like railroads several decades earlier, radio gave armed forces a new capability while providing their enemies with a new target for intelligence gathering. It let armed forces communicate wirelessly over great distances, but enemies could intercept those messages. The information thus obtained came directly from the enemy, generally from high ranks, rapidly (revealing plans before they materialized on the battlefield), and from many sources (providing confirmation and detail). For the first time, therefore, intelligence was timely, voluminous, and trustworthy. And so for the first time, it could regularly help win battles.

In 1914, as the guns of August began to fire, the Kaiser's radiomen overheard Russian transmissions. These enabled General Paul von Hindenburg and General Erich Ludendorff to encircle and destroy an advancing Russian army at Tannenberg in one of the great victories of the war. An architect of that victory, General Max Hoffmann, wrote later, in The War of Lost Opportunities, "We had an ally that I can only talk about after it is all over -- we knew all the enemy's plans. ... The Russians sent out their wireless in clear [without codes]." That helped Germany succeed on the eastern front in general. "We were always warned by the wireless messages of the Russian staff where troops were being concentrated for any new undertaking," Hoffmann wrote. Because the war in the east ended with the Bolsheviks' seizing power in Russia, a result of the country's defeat by Germany, one could say that the course of twentieth-century history was shaped in part by radio intercepts.

Likewise, imperial Germany's ally Austria-Hungary enjoyed great cryptanalytic success in its battles with Italy. A postwar Italian commission of inquiry into the catastrophic defeat at Caporetto, in October and November 1917, in which German and Austro-Hungarian forces broke the Italian lines, killing 40,000 Italian soldiers and capturing more than 250,000, found that a key reason for the disaster was that "the enemy had found the keys to almost all [Italy's] codes, even the most difficult and most secret."

Communications intelligence helped the Allies at least as much. On the western front, a brilliant young French army officer pushed cryptanalysis to the limit to break the field cipher that Germany had introduced in March 1918 for use in planning what Berlin hoped would be a war-winning offensive. The solution of a June 3 cryptogram revealed the Germans calling urgently for ammunition, presumably for an attack. Radio direction-finding subsequently disclosed the location of German troops. So alerted, the French repelled Germany's last offensive spasm.

In August 1914, the Russians found a naval codebook in a stranded German cruiser in the Baltic and loyally presented it to their British ally, enabling London to read the messages and forestall the movements of Germany's High Seas Fleet. Thus taught cryptanalysis, the British learned how to break Germany's diplomatic codes and achieved the greatest intelligence coup of all time: In 1917, they decrypted the telegram containing German Foreign Minister Arthur Zimmermann's foolish and fateful suggestion that Mexico attack the United States in an effort to regain its lost territories of Arizona, New Mexico, and Texas. The United Kingdom handed this propaganda weapon to President Woodrow Wilson. Six weeks after Wilson made it public, the United States entered the war.


At last the major powers, realizing that intelligence could contribute critically to military victory, took it seriously. Countries that had not possessed cryptanalytic agencies in 1914 but that had established them during the war -- such as Germany, Italy, the United Kingdom, and the United States -- retained them afterward. Intelligence had been institutionalized everywhere. And the paradigm of defeat begetting a permanent, peacetime intelligence-evaluation unit recurred. In its post-Versailles general staff, Germany finally established such a branch.

The significance of intelligence increased as the century progressed. During the Washington Conference of 1921­22, an international gathering called by the United States to limit the naval arms race and work out security agreements in the Pacific, diplomats used information that the U.S. Cipher Bureau had obtained from Japanese cables to push Japan to accept a smaller naval force than Tokyo had wanted. By stopping a naval arms race, this saved many countries many millions of dollars.

During World War II, intelligence -- again chiefly as code breaking -- shortened the war. In the Atlantic theater, the solution of the main German cipher machine, the Enigma, enabled the Allies to steer their convoys around the U-boat wolf packs. In June 1942, the U.S. Pacific Fleet exploited its ability to read Japanese naval codes to defeat a Japanese fleet at Midway. The spectacular April 1943 midair assassination of Japan's premier strategist and the planner of the attack on Pearl Harbor, Admiral Isoroku Yamamoto, stemmed directly from the solution of encrypted communications containing his flight itinerary. Other coded messages told U.S. submarines the positions of enemy convoys; the convoys' subsequent sinkings brought Japan close to industrial impotence and starvation. By using cryptanalysis to discover Hitler's plans for an August 1944 counterattack in Normandy, Allied intelligence helped block it and destroy half of two German armies around the French town of Falaise. Although it is impossible to quantify the impact of intelligence on the war, some historians claim it hastened the end of the conflict by two years.

Many of the battles won by intelligence in both the world wars were defensive -- not surprisingly, since "awaiting the blow" is, as Clausewitz said, the "characteristic feature" of defense. Between the wars, the states that were not preparing for aggression built up their intelligence capabilities the most. Poland cracked the German Enigma cipher machine; the United States broke the main Japanese diplomatic cipher machine. Countries bent on attack concentrated on weapons -- troops, tanks, planes. Hitler never combined his half dozen code-breaking agencies into one, nor did he demand results from his spy agency. These oversights did not pose a problem for his blitzkriegs, but they came back to haunt him when the war turned and he found himself on the defensive, unable to anticipate where the Allies were going to attack next.

During the Cold War, both sides feared attack, and once again a concentration on defense spurred an interest in intelligence. Spies are said to have warned the United States about Soviet initiatives. U.S. U-2s photographed Soviet missiles in Cuba in 1962. Satellites revealed silo construction, missile launches, and nuclear tests around the world. It may not be too much to say that intelligence helped maintain the balance of terror and kept the Cold War from becoming hot. And since then the opportunities for intelligence have multiplied with the information revolution and the advance of technology.

Over time, the growing importance of intelligence translated into more prestige for intelligence specialists. Higher ranks were one obvious manifestation of this trend. Before World War II, the G-2 (the chief intelligence officer) in the U.S. War Department's general staff was often a colonel, while his counterparts in other disciplines were always generals. During the war, however, intelligence officers got promoted. The chiefs of the army and navy intelligence divisions, the heads of the army and navy units producing communications intelligence, the G-2s for Dwight Eisenhower, the supreme commander of Allied forces in Europe, and Douglas MacArthur, the supreme commander of Allied forces in the Southwest Pacific -- all became general officers or flag officers. They did not have the responsibility or the rank of commanders leading fighting men, but intelligence work no longer limited their prospects for advancement. During the Cold War, the process went even further, as officers advanced from careers in intelligence to the command of combat troops. In 1978, for example, General Lew Allen became chief of staff of the U.S. Air Force after having served as head of the code-breaking National Security Agency. Other examples abound. Indeed, so much has the taint of intelligence faded that a former director of central intelligence has been elected president of the United States.


With the end of the Cold War, the intelligence establishment in the United States, along with the rest of the national security community, seemed at a loss. A geopolitical environment no longer structured by a highly militarized confrontation with a fixed opponent raised new challenges. During the 1990s, intelligence budgets and capabilities dropped, even though computer technology provided ever more data for collection and analysis.

Then came 9/11. Just as the defeats of the nineteenth century had bred intelligence-evaluation agencies and Pearl Harbor had spawned the CIA, so the attacks on the World Trade Center and the Pentagon led to the creation of the Office of the Director of National Intelligence. This time the enemy was not a state but an amorphous collection of radical individuals and groups bent on causing catastrophic damage. The resulting "war on terror" has featured intelligence in a starring role. This development was to be expected, given the enemy's unpredictability and the inherently defensive nature of the struggle. But just what functions intelligence establishments can and should assume in the conflict is hotly contested -- both because of the small, agile, and unconventional profile of the targets and because operational demands have essentially erased the divide between domestic and international covert activities that had enabled Western publics to feel comfortable with the poking and prying of the agencies working on their behalf. The failure to detect the relatively moribund state of Saddam Hussein's weapons of mass destruction programs, moreover, has given the intelligence community another black eye.

Far from being disrespected as they once were, intelligence gathering and analysis are now considered such indispensable government functions -- and so much is expected of them -- that their inability to disperse the fog of war or of international politics causes outrage. The irony is that even though intelligence has come of age, it will inevitably fall short of the public's expectations, no matter what resources and attention it receives, because of the irreducible unpredictability of its targets. And no matter how accurate intelligence is, it will be useless if ignored.

Moreover, information cannot win wars by itself. Information helps commanders make their operations more effective and efficient. It magnifies physical resources by enabling troops and guns to be better used in combat. It improves will and morale by reducing anxiety and steadying command. But ultimately its effect is secondary: it works only as a multiplier and guider of force and determination. If the Axis had possessed the best intelligence and the Allies the worst, the Allies still would have won.

It is possible that in the new and strange kind of war currently being fought, with the extraordinary premium that is placed on timely and accurate information to ward off attacks and to track down the enemy, intelligence may play an even greater role in national security than ever before. But even then, it will never be decisive on its own. Strength is. Ulysses may have been the cleverest of the Greeks and the one who understood best the purposes to which intelligence can be put. But in the end not even he relied on it to recover his kingdom. He slew his enemies with a bow that only he was strong enough to string.

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  • David Kahn is the author of "The Codebreakers" and other books on intelligence and a founding editor of the journal Cryptologia.
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