Puzzlers At War

The brilliant mathematicians and crypto-analysts sat at long tables working to decode the ciphers with pencils and paper. Each labored through some of the thousands of possible permutations. Sometimes by sheer luck, but more often through perseverance, the secrets were unlocked and withdrawn from the coded messages. But it took time and that was something in short supply.

During World War II, the Germans used the most sophisticated encoding machine of its time. Dubbed ENIGMA, it was initially developed for commercial purposes in the 1920's. Then the German military, seeing its potential, bought the patent and it became the mainstay of their encoding operations.

The Allied forces depended heavily on materiel shipped from the Americas. Unfortunately, the supply convoys were at the mercy of marauding German U-boats which roamed the North Atlantic shipping routes in 'wolf-packs'. The losses of men and machinery mounted until only a small percentage of ships were arriving safely in England. Merchant ship losses to U-boats in any one month could be a staggering 100 ships. By 1941, the British OIC (Operational Intelligence Center) estimated that there were almost 200 German U-boats (though not all at sea). America threatened to withhold her life-saving supplies unless Britain could guarantee a greater level of protection. Congress demanded an investigation into the failures of intelligence and convoy operations. The pressure was on and Britain and the Allied Forces needed a breakthrough.

That breakthrough finally came on May 9, 1941 with the capture of an Enigma machine, operation manuals, and setup data from a disabled submarine, U-110. British Intelligence already had models of older Enigma machines (which came to them courtesy of the Poles) and most German transmissions were being intercepted and consistently decoded. However, more recent Enigma machines had been improved and the ciphers were increasingly complex and, hence, took more time to decode. The longer the decryption time, the greater the losses to the wolf-packs.

Furthermore, the German submarine system (the submarine version of Enigma was code named DOLPHIN), employed modified logic and resisted decryption. The capture of U-110 and the subsequent retrieval of its Enigma machine would prove to be a turning point in the war. It allowed the Allied Forces to neutralize the submarine threat in the Atlantic and thereby safely deliver life-saving supplies to Britain. Incidentally, it also played a pivotal role in the defeat of Rommel in North Africa. His supply ships were being sunk as they crossed the Mediterranean.

The captured codes and paraphernalia from U-110 were delivered to Camp X (Bletchley Park) where as many as 10,000 people were employed in a secret operation code named ULTRA (considered the best kept secret of the war). Of these, hundreds were cryptographers who toiled night and day to decode the steady stream of German wireless communications. Fortunately for them, there were a few things which worked in their favor.

One was the absolute belief in the infallibility of the Enigma machine in the minds of the German command. As late as 1943, Germany still didn't know that Enigma had been compromised. Another was the methodical nature of the German military. U-boats were rarely permitted to attack on initiative or to deviate from orders without permission from headquarters and were always required to report their position.

Lastly (and perhaps the most fortunate give-away), the transmissions usually contained some text which was common to all messages; either a salutation or a signing-off. This made for certain repetitive patterns which, once located, gave the cryptographers keys to deciphering the rest of the text.

Manpower alone was not enough to defeat the German Enigma machine. On just a three-rotor machine, there were 150,000,000,000,000,000,000 possible settings. To add to their woes, the Brits learned of TRITON; a four-wheel Enigma variant (code named SHARK) that was replacing all three-wheel Enigma systems. It was being distributed throughout the German Navy, including the submariners.

The code breakers had to find which one of this vast number of settings had been used before they could decipher a message. The Turing Bombe, a very powerful search engine envisioned by the brilliant mathematician, Alan Turing, was developed to tackle this problem. It expanded an original idea of Marian Rejewski, a Polish code breaker who called his device a Bomba. The Turing Bombe is now considered the forerunner of the modern computer.

Then a stroke of luck! A U-boat transmitted a message which was encrypted with the SHARK system before it had been authorized for use. Realizing the error, the U-boat transmitted the same message re-encrypted with DOLPHIN. This single procedural security faux pas saved untold effort in solving the SHARK four-wheel logic. Having the two encrypted versions of identical text was all that was needed to reverse engineer the SHARK system logic.

The cryptographers at Bletchley Park were not only decoding messages but also developing their own encryption systems. By reading German intercepts they were able to determine that the British cipher system had been broken and it was replaced. Immediately the drop in efficiency of the German U-boats reflected their inability to read the Allied Forces new cipher.

In any conflict, knowledge of the enemy's troop numbers, armaments, and movements are critical to a successful campaign. Soldiers with guns and bombs may defeat an army but it's raw intelligence, subterfuge, and cryptographers who can make the different between winning a battle and winning a war.

Thanks to good fortune and extraordinary brainpower, countless lives were saved and the German Wehrmacht was destroyed. Puzzle solvers had played a decisive role and one can't underestimate their contribution to the war effort.

The Enigma Code Breach

Codes, Ciphers, & Codebreaking

The Enigma Applet
Encode and decode your own messages with this Enigma simulator.

Cryptograms See if you've got what it takes to be a code breaker.