How did the Enigma (a rotor machine used during World War II) help the Allied forces? What was the impact and significance?

The Enigma machine was a type of rotor ciphering machine used by the Nazis during World War II.  Nazi military leaders communicated secret messages using Enigma code.  The Nazi use of the Enigma machine was discovered by the Allies and they were able to use it to their benefit.  The British government established a large secret compound for decoding Enigma codes at Bletchley Park.  The code changed daily, which proved to be a challenge for those who were seeking to decode it.  At times, the code was broken by the codebreakers.  The Germans then made changes to the codes they used, which the Allies had to learn how to decode.  For example, Alan Turing developed an early computation machine called the bombe to help decode messages sent using the Enigma machine.  After that, the German Navy altered their method of code communication.

Enigma codes used by the Nazis were not perfect, and therefore could be cracked.  When the decoders at Bletchley Park were able to decipher the Enigma code, military leaders discovered the plans and movements of the Nazis.  The Italian Navy also communicated via Engima code.  When these codes were broken, the Allies were able to make military decisions that protected troops.  

The British Royal Navy was able to sink many German ships because of the intelligence they received via Enigma code.  The war would most likely have lasted longer if not for the decoding practices at Bletchley Park and among other departments of Allied intelligence.  The use of computing machines, such as Turing's bombe, paved the way for the development of future computers.