The secret war behind D-Day: How breaking Enigma changed history

The Allied forces crossed the English Channel on 6 June 1944 and landed on the shores of Normandy to begin the liberation of Europe. Eleven months after D-Day the Nazis surrendered but victory could have taken much longer and the loss of life far greater had it not been for one tightly guarded secret.

Both the Axis and Allied powers used machines to encrypt their messages. However, neither Germany nor Japan knew that their codes had been broken.

What was the German Enigma machine?

Germany’s Enigma machine was developed in 1918 to protect banking transactions. However, the device was repurposed for the war effort. Those used by Nazi forces mainly consisted of a keyboard, three rotors and a panel of letters that lit up.

How breaking Enigma changed history

The Germans believed the codes sent between Enigma machines were unbreakable. However, early on in the war the Allies were already reading intercepted messages encrypted by Enigma devices, a fact that they keep closely guarded throughout the war.

Thie codes were originally broken thanks to German traitor who helped Polish cryptanalysts copy an Enigma device and solve the letter-scrambling patterns. This knowledge was shared with the Allies and together a team led by Alan Turing improved the ability to decrypt German Enigma codes.

This helped to reduce the efficacy of the German U-boats disrupting transport shipments until a fourth wheel was added to German navy Enigma machines in 1942. However, with the capture of secret code books, cryptanalysts once again were able to stymie German submarines operations in the Atlantic.

When the Allies launched the D-Day invasion, officials knew of the exact locations of German forces waiting for them in the Normandy. Additionally, intercepting and decrypting German communications provided faster updates on the progress of Allied troops than their own communication lines.

The breaking of the Enigma codes as well as those used by Japan is credited with substantially shortening World War II, by as much as two years according to some estimates. It also saved countless lives by making it safer for transport ships to cross the Atlantic, know where air raids were planned and being able to pinpoint where German positions were.

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