I did not speak out

Here is a poem from Nazi-era Germany. I learned of it from the book "I am Malala".

First they came for the communists, and I did not speak out - because I was not a communist;
Then they came for the socialists, and I did not speak out - because I was not a socialist;
Then they came for the trade unionists, and I did not speak out - because I was not a trade unionist;
Then they came for the Jews, and I did not speak out - because I was not a Jew;
Then they came for the Catholics, and I did not speak out - because I was not a Catholic;
Then they came for me - and there was no one left to speak out for me.