The cryptanalytic confrontation of World War II became a typical example of a battle of minds with a famously twisted plot. Here is a detective, a thriller, and a spy thriller in one set.
On June 4, 1941, the German ship Gedania fell into the hands of the British, about which the Germans had no idea for a long time. They raised the panic when they captured several sailors from that same British destroyer. And, although the Gedania team worked perfectly and destroyed everything connected with the Enigma in time, the Germans could not know about it.
But the British could not hide the capture of the U-570 submarine in August 1941, and the top of the German Navy was seriously concerned about it. Doenitz in this regard turned to Erhard Martens, the head of the communications service of the German fleet, for clarification. Martens created a whole theory why Doenitz should not worry so much about the discrediting of ciphers. The fact is that the last communication with the U-570 went very badly - the submarine could not fully receive messages. And Erhard considered this as direct evidence that the team had already begun at that time to destroy the Enigma itself and all the accompanying documentation. Doenitz, as he had repeatedly before, believed in such fabrications and calmed down. Literally a month later, the German submarine "U-501" was forced to surface and surrender to the mercy of the British. But they could not find anything valuable - the German submariners managed to clean everything up in time. And, importantly, the capture of U-501 remained a secret for the German command, despite the busy Kriegsmarine traffic in this square.
An obvious failure of the entire Ultra's conspiratorial scheme was the operation to destroy the German submarines U-67, U-68 and U-111 off the African coast. The data was obtained from the interception of the Enigma, and the Admiralty decided not to let this chance pass. One British submarine was sent to the targets, which, without completing the assigned task, barely left the area with heavy damage. The Germans, of course, immediately noticed such a "successful" appearance of an English submarine at a considerable distance from the base. By chance, she could not stumble upon a cluster of German submarines off Africa, which means that somewhere there is a serious leak of information. Martens, who either did not want to get involved with the replacement of "Enigma", or he openly harmed the Germans, tried to convince the suspicious Doenitz again. But then on November 22 and December 1, the British sent two supply vessels to the bottom at once - "Atlantis" and "Python". Moreover, the British cruisers did it at the point of meeting of the ships with the wards of the submarines of the German fleet.
Admiral Kurt Frike
Admiral Curt Fricke, investigating the circumstances of the deaths of the two ships, assumed for some time that England received the information from the Enigma ciphers. But we could not find at least a hint of this from the decrypted messages of the Admiralty, and this version was discarded. Moreover, in February 1942, the British screwed up when they let the German strike group of the battleships Scharnhorst, Gneisenau and the cruiser Prince Eugen slip through the English Channel to the ports of Norway. A month earlier, the legendary "Tirpitz" was capable of such a trick. Now there was a direct threat to convoys to the USSR and England from these giants, but the Admiralty simply did not have time to do anything - the information from Bletchley Park came too late. Who knows, maybe the preemptive actions of the British fleet in these battleships stories could finally convince the Germans that Enigma was hacked long ago? But the German leadership only once again reassured itself about its own cryptographic inaccessibility.
The following fact speaks volumes about the level of German confidence in their own encryption system. In September 1942, an English destroyer was captured, on which the routes of the German convoys were discovered. It would seem that this is obvious proof of the presence of either an extensive spy network in their rear, or a powerful decryption apparatus among the British. But in response to such a find, only the key settings of Enigma were changed.
With all this, in the German naval command there was a group of analysts who monitored all movements of warships at sea. The purpose of their work was to look for signs that the British knew in advance about the routes of the German fleet, avoiding contact, or deliberately attacking with superior forces. But for the entire time of the work, a minimum of hints of such signs were found. What is this - the professionalism of the British or the incompetence of the German General Staff?
Over time, Doenitz began to receive information about the possible discrediting of "Enigma" already from other departments. In August 1943, the Abwehr reported to the Grand Admiral intelligence from Switzerland, which indicated the ability of the Allies to read German naval codes. In particular, a source from the US Department of Defense disclosed data on the decryption of orders to submarines of the Third Reich. Moreover, this was fully justified by the situation in the naval theater of operations. From June 12 to August 1, the enemy tried to place about 50% of the encounters of German submarines in the open ocean, and from August 3 to 11, all such encounters were interrupted. It would seem that everything, it's time to send "Enigma" for recycling. But Karl Doenitz, for some inexplicable reason, accepts the version that the enemy has once again obtained the key installations of the encryption machine. According to the communications service, the British would not be able to hack the Enigma, all leaks are associated with treason or forcible seizure of keys. The Grand Admiral was not convinced by the new portions of intelligence from Switzerland, in which they referred to a certain American from the naval delegation who was aware of a certain British decryption program. Probably, if he had indicated the name "Ultra" and all participants in the project by name, all the same the Germans would have shown truly Aryan staunchness in defending the honor of "Enigma". Here, the chief cryptanalyst of the Wehrmacht Karl Stein played into the hands of the Allies, authoritatively declared after the study of the Enigma: it is possible to hack, but it will take a lot of time. Karl Stein did not know that in England the prototype of the computer "Bomb" has been ticking for a long time, speeding up the decryption by orders of magnitude.
Then the story went in a spiral. The British once again risked the secrecy of Ultra, making it clear that they know about the location of critical resources for the Germans, and in Germany they only changed the key settings of the Enigma. This happened at the beginning of 1944, when the Admiralty learned from the data of Bletchley Park about the location of the German tanker Charlotte Schliemann (on February 12 it was sunk in the Indian Ocean). A month later, following a similar tip, the second tanker, Braque, went to the bottom.
In 1944, Doenitz shared his misconceptions with the paper: “With the exception of two or three doubtful cases, the conclusions of the British were based on information readily available to them about our submarines, on the radio direction finding data of the operation of their radio stations and on the data of boat traffic in combination with a quite feasible process logical deduction. The most important result of our research is indisputable proof that with the help of aircraft equipped with radar, the enemy is capable of revealing the dispositions of our submarine forces with sufficient accuracy and, accordingly, changing the direction of movement of his convoys … boats to various bases, about the time of their departure to the sea and return to the bases, and, possibly, also about the areas of operations at sea intended for boats."
In general, both Doenitz and his headquarters overestimated the capabilities of aerial reconnaissance, photographing and detecting German submarines using aircraft and ship radars. Until the very end of the war, the communications service managed to dispel the Grand Admiral's doubts about the reliability of the Enigma.
The experts of the surveillance service met the collapse of the Third Reich in the city of Flensburg in northern Germany in the hope of successfully surrendering to the Americans and British. This was in the interests of our Western allies as well - German cryptographers knew too much about British ciphers and no one wanted to share this with the Russians. As a result, all German naval archives were transported to London. Their analysis showed that the successes of the German cryptanalyst were not much greater than the British had expected.
