Ultra also gave Western intelligence a glimpse of the location and strength of German fighter units, as well as the effectiveness of attacks carried out by Allied tactical aircraft on German air bases. Furthermore, these intercepts indicated when the Germans had completed repairs on damaged fields or whether they had decided to abandon operations permanently at particular locations. Armed with this information, the Allies pursued an intensive, well-orchestrated campaign that destroyed the Germans’ base structure near the English Channel and invasion beaches. These attacks forced the Germans to abandon efforts to prepare bases close to the Channel and instead to select airfields far to the southeast, thereby disrupting German plans to reinforce Luftflotte 3 in response to the cross-Channel invasion. When the Germans did begin a postinvasion buildup of Luftflotte 3, the destruction of forward operating bases forced it to select new and inadequately prepared sites for reinforcements arriving from the Reich. Ultra intercepts proceeded to pick up information on much of the move, which indicated bases and arrival times for the reinforcing aircraft. Another substantial contribution of Ultra to Allied success was its use in conjunction with air-to-ground attacks. Ultra intercepts on June 9 and 10 revealed to Allied intelligence the exact location of General Leo Geyr von Schweppenburg’s Panzer Group West headquarters. Obligingly, the Germans left their vehicles and radio equipment in the open. The subsequent air attack not only destroyed most of Panzer Group West’s communications equipment but also killed seventeen officers, including the chief of staff. The strike effectively eliminated the headquarters and robbed the Germans of the only army organization they had in the West that was capable of handling large numbers of mobile divisions.

Subscribe Today

• Did you enjoy our article?
• Read more in MHQ magazine
• Subscribe online and save!
 

Why were the British able to break some of the most important German codes with such great regularity and thereby achieve such an impact on the course of the war? The Germans seem to have realized midway through the conflict that the Allies were receiving highly accurate intelligence about their intentions. Nevertheless, like postwar historians, they looked everywhere but at their own encrypted transmissions. Enthralled with the technological expertise that had gone into the construction of Enigma, the Germans excluded the possibility that the British could decrypt their signals. After the sinking of the great battleship Bismarck in May 1941 and the rapid clearance of the supply ships sent out ahead of her from the high seas, the Kriegsmarine did order an inquiry. Headed by a signals man (obviously with a vested interest in the results), the board of inquiry determined that the British could not possibly have compromised the Enigma system. Rather, the panel chose to blame the disaster on the machinations of the fiendishly clever British secret services. By 1943, the success of British anti-submarine measures in the Atlantic once again aroused German suspicions that their ciphers had been compromised. In fact, the commander of U-boats suggested to German naval intelligence that the British Admiralty had broken the codes: B.D.U [the commander of U-boats] was invariably informed [in reply] that the ciphers were absolutely secure. Decrypting, if possible at all, could only be achieved with such an expenditure of effort and after so long a period of time that the results would be valueless. One British officer serving at Bletchley Park recalled that German cryptographic experts were asked to take a fresh look at the impregnability of the Enigma. I heard that the result of this ‘fresh look’ appeared in our decodes, and that it was an emphatic reassertion of impregnability.

The Germans made a bad situation worse by failing to take even the most basic security measures to protect their ciphers. In fact, a significant portion of Bletchley Park’s success was due to procedural mistakes that the Germans made in their message traffic. Among basic errors, the Germans started in midwar to reuse the discriminate and key sheets from previous months rather than generate new random selection tables. If that were not enough, they (particularly the Luftwaffe) provided a constant source of cribs, which were the presumed decrypted meanings of sections of intercepted text. They enabled the British to determine Enigma settings for codes already broken. The cribs turned up in the numerous, lengthy, and stereotyped official headings normally on routine reports and orders, all sent at regular times throughout the day. According to Gordon Welchman, who served at Bletchley Park for most of the war, We developed a very friendly feeling for a German officer who sat in the Qattara Depression in North Africa for quite a long time reporting every day with the utmost regularity that he had nothing to report.

Help HistoryNet by bookmarking to