I remember never understanding the 'trade unions' part of this poem as a kid when we studied it in history class, today it sure seems to make sense. From Wikipedia: "Martin Niemöller was a German pastor and theologian born in Lippstadt, Germany, in 1892. Niemöller was an anti-Communist and supported Hitler's rise to power at first. But when Hitler insisted on the supremacy of the state over religion, Niemöller became disillusioned. He became the leader of a group of German clergymen opposed to Hitler. Unlike Niemöller, they gave in to the Nazis' threats. In 1937 he was arrested and eventually confined in the Sachsenhausen and Dachau concentration camps. His crime was "not being enthusiastic enough about the Nazi movement."'
First they came for the communists,
and I didn't speak out because I wasn't a communist.
Then they came for the trade unionists,
and I didn't speak out because I wasn't a trade unionist.
Then they came for the Jews,
and I didn't speak out because I wasn't a Jew.
Then they came for me
and there was no one left to speak out for me.
-Pastor Martin Niemoller