Bertolt BrechtBertolt Brecht (1898-1956) is sometimes considered the champion of Expressionist theater, however he moves beyond this and created the "didactic" theater. He rejected the traditional concept of identifying the audience with what happens on stage; they must not get caught up in dramatic illusion but maintain a subjective distance so that they can arrive at rational judgments about the matter being presented.
His first play, written in 1922, was an Expressionist drama about a returning war veteran unable to adjust to postwar society. Brecht was a Marxist, and because of this, he went into exile in 1933 - this is when his rise to fame began. He eventually came to the United States, and wrote many plays including the Kaukasische Kreidekreis [the Caucasian Chalk Circle] which probed the discrepancies between law and justice. The play was performed at Columbia University recently and an article was in the New York Times May 25, 1998. http://www.nytimes.com/library/theater/052598chalk-theater-review.html
Brecht decided to leave the US after he was brought before the Committee on Un-American Activities in 1947 because of his involvement in communism. He went back to Germany and settled in East Berlin where he founded the Berliner Ensemble and devoted his efforts to building up a theater based on his dramatic theories. The Berliner Ensemble still exists and a program of plays can be found at http://www.berliner-ensemble.de/ In spite of his great success in previous years, his artistic creativity began to "dry up." He died on August 14, 1956 in East Berlin.
Some more brief descriptions of his plays can be found at: http://www.thomson.com/routledge/who/germany/brecht.html