The British Evacuation of Norway

Early in World War II, the British position in Norway became untenable, and they decided to remove their forces. (Featured image: The HMS Glorious)

The operation to accomplish this task took place in Narvik, Norway. It was supported by the aircraft carrier HMS Glorious, which evacuated pilots and planes. British T/A produced indications that German naval units were transiting into the North Sea and in all likelihood were prepared to engage in hostilities. These reports, some as early as two weeks before the engagement, were sent to the British Admiralty which, having little understanding of T/A, dismissed the reports as unproven and failed to send the warning to the Glorious. In fact, the German battle cruisers Scharnhorst and Gneisenau were moving into the North Sea and about to engage the Glorious. Had the Glorious received the warning, she might well have sent out defensive patrols and even attacked the German cruisers with her torpedo planes. The captain of the Glorious, however, not having received the intelligence reports, was totally surprised by the German presence.

This fact, added to several incompetent moves on his part, led to his ship being sunk before he could get a message off to his headquarters that he was under attack. Ironically, the British learned of the disaster by reading German messages reporting the sinking of the Glorious. This painful lesson clearly illustrated the value of T/A and the consequences of not using it properly.(25) The British did give much greater credence to COMINT after this unfortunate incident.(26)

German Use of Traffic Analysis

The Germans used COMINT extensively in WWII, and they were fully aware of its value. Their efforts in WWII were based upon their WWI experience, which led them to make a strategic decision at the outset of WWII to emphasize efforts against low-level and medium-grade cipher systems rather than dedicating scarce resources on the slim possibility of exploiting high-grade ciphers. The Germans were quite successful in attacking medium- and low-grade cipher systems. (27) Further, their attempts to produce information through T/A, along with RDF and reading operator chatter and other low-level clear text traffic, yielded the major source of their tactical intelligence information during the war.(28) Some examples follow.

The Germans had mounted an offensive in the Crimea on the Black Sea and were moving against the port at Sevastopol. The Soviets levied counterattacks against the Germans, but the Germans had intercepted wire communications, allowing them to save two of their patrols from annihilation. The same source on another day gave warning to the Germans of two Soviet attacks on their position. Both were repulsed, and after the second attack, they counterattacked with an artillery barrage.(29)

In another case the Soviets attempted to spoof the Germans, but one experienced German intercept operator detected the ruse. A Soviet army unit was moving to Stalingrad and left a communications group at its original position. The unit maintained its communications pattern, indicating to the Germans that the Soviet unit remained in its original location; however, one of the communications operators, who moved with the Soviet army, made the mistake of transmitting from his new location. The astute German intercept operator recognized the Russian communicator and warned the

German command that the Soviet unit was actually moving toward Stalingrad. The Germans took appropriate defensive measures.(30)

Another source of information accessed by the Germans was obtained by monitoring British exercise activity. A prevailing assumption was that the way a military unit exercises indicates how it will fight. The Germans copied communications associated with British amphibious landing exercises and determined what the British were planning. The information gleaned included the size of the proposed landing area, the number of units the British would commit in the initial assault, and how deep they planned to penetrate on the first day.(31)

The Germans used T/A to provide tactical information to their troops in France after D-Day in Normandy. They identified and located many American units including the 1st U.S. Army with four corps and fifteen divisions, the VIII Corps, the 101st and 82nd Airborne Divisions, and the 90th Infantry Division. Further, the Germans followed the movement of the U.S. XIX Corps, predicting that the Corps would attack in the identified location. The Germans took actions based on this information and significantly slowed the American advances.(32)

Also in Normandy, German troops received information from communications sources that warned them of Allied bombing runs. The Germans intercepted British requests for air support and were able to determine areas/targets and times of the planned strikes. Consequently the Germans were often able to move their units away from the target areas with a great saving of lives and equipment.(33)

Early in WWII German field commanders did not hold T/A in high regard, but as the war pressed on they considered it their best source of intelligence information. For instance, the G2 of the 40 Panzer stated, in referring to the usefulness of the T/A product, the corps “always knew almost exactly the enemy situation, location and strength. This knowledge contributed considerably to the complete annihilation of the Popoff armored army.” Other commanders stated that T/A was “the most important means for clarifying the enemy picture,” “the most important of the sources,” and “the most copious and the best source of intelligence.”(34)

Notes 25-34

25. Ibid., 141.
26. Stephen Budiansky, Battle of Wits: The Complete Story of Codebreaking in World War II (New York: Touchstone, 2000), 46-49.
27. David Kahn, Hitler’s Spies: German Military Intelligence in World War II (New York: Macmillan, 1978), 189-212.
28. Ibid., 200.
29. Ibid., 189.
30. Ibid., 203.
31. Ibid., 204.
32. Ibid., 207.
33. Ibid., 208.
34. Ibid., 210.

Source: Center for Cryptologic History National Security Agency