What is a hero?

We usually think of a hero as a soldier, a fireman, a policeman, someone literally risking his life for a noble cause. Sometimes a hero can be a quiet person doing a secret job that no one ever finds out about, but that has an enormous impact on a heroic enterprise. Meet Marian Rejewski. Marian was a Polish mathematician who used his mind to solve the cryptography behind the Nazi Enigma code machine during World War II. It will never be known how many lives were saved by the work of this quiet, brilliant man.

http://en.wikipedia.org/wiki/Marian_Rejewski