When we think of martyrs, we often go back to the early Christians as the typical examples - dying for the idea that they should worship one God and no other. Another often quoted example is Socrates - dying for the idea of open enquiry. I know that people have died throughout history but I am looking to see if there are earlier examples that fit the definition:
a person who sacrifices something of great value and especially life itself for the sake of principle.
I'm looking for specific people or groups of people that died a martyr's death (either in historical fact or literature). To attempt to hone the definition further, I am looking for people who placed an idea before their own safety or the safety of their kin and who had the choice to act otherwise.