moment in the North African fighting. There was no time to have the ships properly spotted beforehand. The decision to attack solely on Ultra intelligence went directly to Churchill. The ships were all sunk by an attack "out of the blue", arousing German suspicions of a security breach. To distract the Germans from the idea of a signals breach (such as Ultra), the Allies sent a radio message to a fictitious spy in Naples, congratulating him for this success. According to some sources the Germans decrypted this message and believed it. In the Battle of the Atlantic, the precautions were taken to the extreme. In most cases where the Allies knew from intercepts the location of a U-boat in mid-Atlantic, the U-boat was not attacked immediately, until a "cover story" could be arranged. For example, a search plane might be "fortunate enough" to sight the U-boat, thus explaining the Allied attack. Some Germans had suspicions that all was not right with Enigma. Admiral Karl Dönitz received reports of "impossible" encounters between U-boats and enemy vessels which made him suspect some compromise of his communications. In one instance, three U-boats met at a tiny island in the Caribbean Sea, and a British destroyer promptly showed up. The U-boats escaped and reported what had happened. Dönitz immediately asked for a review of Enigma's security. The analysis suggested that the signals problem, if there was one, was not due to the Enigma itself. Dönitz had the settings book changed anyway, blacking out Bletchley Park for a period. However, the evidence was never enough to truly convince him that Naval Enigma was being read by the Allies. The more so, since B-Dienst, his own codebreaking group, had partially broken Royal Navy traffic (including its convoy codes early in the war), and supplied enough information to support the idea that the Allies were unable to read Naval Enigma. By 1945, most German Enigma traffic could be decrypted within a day or two, yet the Germans remained confident of its security. Role of women in Allied codebreaking After encryption systems were "broken", there was a large volume of cryptologic work needed to recover daily key settings and keep up with changes in enemy security procedures, plus the more mundane work of processing, translating, indexing, analyzing and distributing tens of thousands of intercepted messages daily. The more successful the code breakers were, the more labor was required.