Code-breaking in World War II

Code-breaking played an important role in the success of the allies in WWII as it informed the British about German advances into the Soviet Union and America would not have won the Pacific War with Japan had it not been for the skill of their code breakers.

Codes were essential to the military and especially to the navy and air force in World War II.  Captains pilots and commanders would have to exchange messages through radio, but the problem was that if the enemy was tuned to the same radio frequency they could intercept the message and know exactly what the other was going to do so they could surprise them.  That is why they needed to encrypt their message so that only their own friendly ships, planes or generals who had the code would know what to do.

There were many methods of encryption that were utilized in World War II. The Germans had a machine called the Enigma.  The Enigma looked like a typewriter, but for every letter you entered it would pass through three rotors that changed it too another than it would reflect back and go back through the rotors again to spit out a new letter. This code was cracked on July 9th of 1941 by British cytologists. They were able to crack it because the enigma never returned the same letter so they were able to narrow down the rotor possibilities. There other clue came from the fact that the Enigma reflected the code.  By spending a lot of time looking and thousands of intercepted German codes they were eventually able to come up with their own machine called the Bombe that returned the original message.  This was helpful because it allowed the British to intercept German commands about how they would attack the Soviet Union.  They also confirmed their fears about the concentration camps which previously not many had actually believed.  This led to an increased motivation and scene of urgency to win the war.

The Japanese used another type of encryption that used a code book not a machine.  Their code was called JN25 and it had a code book of 90,000 words and phrases.  Code breakers at station HYPO were tasked with solving this code.  After using cross referencing between thousands of messages and by seeing which characters occurred the most, they were able to decipher many of the phrases of the code book and compiled a big list.  With this knowledge they then learned that there was an impending attack on a mysterious location encoded as "AF" but they did not know where that location was.  They were able to crack the code when they sent a non-encoded message that said that the desalinization plant on Midway Island was down.  This was intercepted by the Japanese and encoded and sent by them saying that "AF's desalinization plant was down.  Thus, they knew that an attack was coming at Midway islands and were prepared.  The result was that they crushed the Japanese at the Battle of Midway and sunk all of their destroyers.  The Japanese could no longer be a major power in the Pacific and that led to there defeat in the war.

Code-breaking played a very important role in the success of the Allies during WWII.  It also led to the development of early computers as the Enigma was very similar to a computer and the code-breakers of HYPO used IBM punch card sorting machines.