Dietrich Bonhoeffer (1906 - 1945) was a major writer and thinker in Germany between the wars. His many books of theology are still read and as influential among contemporary evangelical believers as the works of C.S. Lewis and Billy Graham: such works as The Cost of Discipleship, Letters and Papers from Prison, Ethics, Life Together, and Christ the Center. In 1939 he refused to take the loyalty oath to Adolf Hitler. Shortly after, he was invited to participate in a plot to assassinate Hitler. He was eventually caught, imprisoned, and executed.