Traffic analysis has been of key importance in providing current information to U. S. military commanders on the identity, location, and movement of opposing enemy forces at the tactical and strategic levels. Although some use was made of the discipline as early as the American Civil War, information derived from traffic analysis was critical in influencing and winning many ground, sea, and air battles of World Wars I and II, Korea, Vietnam, Iraq, and other conflicts. T/A also has been useful in supporting diplomatic initiatives, and, especially during the Cold War, it supported counterintelligence, counterterrorism, and counternarcotics efforts, as well as the country’s response to numerous international crises.

World War I

When the American Expeditionary Force (AEF) entered WWI in 1917, it was not schooled in the use of traffic analysis. British and French intelligence services provided the AEF personnel a “crash course” in the art of traffic analysis. The AEF sought “to describe the enemy’s forces, to determine the locations of his units, discover his intentions, and where and when he would carry them out.”(6) T/A was one of the primary sources of intelligence contributing to the satisfaction of these operational requirements.

U.S. radio direction finding vehicle, WWI

Military intelligence improved markedly during WWI, and the sources and methods developed there continued to produce information for decades to come. The static front with its miles of trenches diminished the value of cavalry and espionage as sources. The advent of reconnaissance information from airplanes and more particularly T/A of enemy communications filled the intelligence gap by providing accurate and timely information.(7)

Army and Air Corps

There were three main means of electronic communications used by ground forces in the front battle lines of WWI. One was radio; another was telegraph on wires; and the other was called a “power buzzer,” a device that sent communications for short distances by using the ground as a conductor. Each was susceptible to being intercepted by the opposition, and traffic analysis was possible on intercept from these sources. It was mainly the advent of radio, however, that brought traffic analysis into the fore.

During 1917 and 1918, T/A may well have been the single greatest source of operational intelligence available to every army on the Western Front.(8) For instance, it has been estimated that T/A, during that period, determined the location of 50-60 percent of the German divisions and military groupings on the British front.(9)

Radio direction finding (RDF), called “goniometry” at that time, also provided critical information on enemy locations (see Illustration 2 showing a direction finding vehicle). One officer described its use in the intelligence process as follows: “Just as naturalists can reconstruct from a few bones a prehistoric monster, which they had never seen, so the goniometric experts are able to gain an amazingly accurate idea of the organization of an army by locating its stations, for the lines of radio communication, which spread fan-wise from army headquarters, form a sort of skeleton, as it were, of the army’s organization, the location of the various stations and their distance from headquarters indicating quite accurately the position of the corps, divisions, brigades, regiments, and battalions.”(10)

Another prominent target of traffic analysis intelligence during WWI was communications supporting the fledgling aircraft activity. Just as with infantry and artillery, the employment of aircraft required radio communications between headquarters and the aerodromes, and those transmissions were susceptible to interception and exploitation.

German spotter aircraft “Roland” used for
reconnaissance early in World War I

One particularly useful application of T/A information was employed against German spotter aircraft. The trench warfare on the front became a battle of attrition, and artillery was a key element in this aspect of the war. Artillery fire was directed in large part through the use of aircraft flying over the battlefield, which would locate high-priority targets, direct artillery fire at them, and assist in calibrating the accuracy of that fire. The British, in particular, used T/A to predict the spotter aircraft flights and, with great effect, direct British intercept aircraft to destroy or disrupt the German flights. These efforts significantly decreased the effectiveness of German artillery.(11) Further, in those instances when the German aircraft got through, the Allied units that were to be targeted by the artillery barrage were warned of possible impending artillery attacks based upon the activity of the aircraft. This warning gave the targeted units some opportunity to take cover and evade fire.

T/A also supported electronic deception, which was practiced during WWI. An army would deliberately send false signals to mislead the enemy into thinking that military units had moved (or not moved). One prominent example was when the British generated a message transmission pattern that led the Germans to believe that the crack Australian and Canadian units remained on the line in Flanders. Under signals silence these units moved to Amiens and participated in an attack that crushed the unsuspecting Germans.(12)

Navy: The Battle of Jutland, May 1916

Early in World War I the British fleet was the dominant force on the high seas. The Germans, on the other hand, were in the process of developing a respectable surface navy. In the spring of 1916, Admiral von Scheer, the new commander-in-chief of the German High Seas Fleet, planned to entice the British Grand Fleet into a sea battle during which he hoped to engage the British fleet in segments and inflict serious losses upon the British without incurring devastating German losses. Meanwhile, the British wanted to counter any German moves, attempting to keep them at bay and inflict whatever damage to the German fleet that they could, without incurring a significant degradation of their own fleet, which they needed to keep intact for the defense of the home islands. One problem the British Navy had at this point was the regular navy’s lack of confidence in the Naval Intelligence arm (Room 40) to support the operational commands in offensive tactical maneuvers. The Room 40 analysts were not permitted to be involved in anything but defensive operations, and were unable to directly communicate with fleet components. Even though the naval intelligence analysts had built a good working knowledge of the organization and operations of the German Fleet, they were not permitted until 1917 to provide any direct support to the British Navy for operational activities.

On May 30, 1916, the two main segments of the British fleet which were in port at Scapa Flow under Admiral John Jellicoe and at Rosyth under Vice Admiral David Beatty, were advised, based on decrypted signals and traffic analysis, that von Scheer intended to put to sea early the next day.(13) That evening, Jellicoe ordered both elements of the Grand Fleet out to sea. Early on the 31st, German battle cruisers left Wilhelmshaven to decoy the British Fleet into the North Sea, with the rest of von Scheer’s High Seas Fleet to follow. It so happened that although von Sheer’s intelligence had alerted him to the deployment of the British Fleet, he decided to proceed as planned. The two components of the British Fleet led by Jellicoe and Beatty, after setting sail on the 31st, were planning to trap the German Fleet based on their earlier intelligence warnings. Unfortunately, the British naval operation was disrupted when the Director of Naval Operations injected himself between the intelligence analysts and the combat commanders.

On the morning of May 31, after the British Fleet had departed Scapa Flow and Rosyth, Rear Adm. Thomas Jackson, the regular navy DNO, made an early and rare visit to his operations center, where he asked the naval intelligence analysts a traffic analysis question. Having seen a report based on T/A that located the callsign DK in port at Wilhelmshaven, Thomas inquired of the meaning of that callsign. With no details provided, the analysts replied that DK was Admiral von Scheer’s personal callsign. Without waiting for clarification or checking further to find that Admiral von Scheer used a different callsign when deploying, while the DK callsign remained at Fleet Headquarters to disguise the Fleet Commander’s movements, Jackson left the ops center to alert Jellicoe and Beatty of his conclusion that the German Fleet was still in port. Shortly after noon on the 31st, the two British commanders received the following cable: “At 12 Noon today, our directional stations place the German fleet flagship ((at its base)) in the Jade. Consider it possible that lack of air reconnaissance may have delayed their start.” Admiral Jellicoe, on receiving this wire, delayed his movement toward the German Fleet, leaving V/Admiral Beatty nearly 70 miles out in front of Jellicoe, where he quickly met the entire German Fleet. Although caught by surprise after the misleading information provided in error, Beatty, though losing two cruisers and suffering serious damage to his flagship, through a brilliant maneuver, lured the German Fleet into the path of the entire British Fleet. Beatty and Jellicoe, with the combined British fleet, then forced the Germans back to port, with neither side sustaining unacceptable damage. Jellicoe, however, missed a splendid opportunity to decimate the German Fleet on its return to port by not using his intelligence fully and by his timidity, stoked by his desire to preserve the British fleet. Even worse, Jellicoe had apparently become jaded regarding the quality of his intelligence and although receiving accurate information on the direction of Scheer’s return route to port, he refused to rely upon it, causing him to miss the opportunity to inflict serious damage to the German fleet. This situation represents a classic instance where solid traffic analysis was misunderstood, misused, and not allowed to provide a potential naval victory which might have altered the outcome of not only a naval operation, but perhaps the war itself.

Notes 6-13

6. John Ferris, The British Army and Signals Intelligence During the First World War, Alan Sutton for the Army Records Society (1992), 3.

7. Terrence J. Finnegan, Col. USAFR (Ret.), “Military Intelligence at the Front, 1914-1918,” Studies in Intelligence 53, no. 4 (December 2009): 25-40.

8. William F. Friedman, Solving German Codes in World War I

(Walnut Creek, CA: Aegean Park Press, 1979), 92.

9. Ibid., 12-16.

10. E. Alexander Powell, The Army Behind the Army (New York:

Charles Scribner’s Sons, 1919), 21.

11. Ibid., 13.

12. Ferris, 21.

13. This incident is described in detail in Christopher Andrew, Her Majesty’s Secret Service: The Making of the British Intelligence Community (New York: Viking, 1986), 102-106; see also R. E. & T. N. Dupuy, eds., The Encyclopedia of Military History From 3500 B.C. to the Present, 1993, 1964, for warning to Jellicoe and Beatty of the sortie of the German High Seas Fleet on 30 May, based on “imprudent German radio chatter”.

Source: Center for Cryptologic History National Security Agency