John Howard Yoder (1927–97) was the leading twentieth-century exponent of the Mennonite theology of non-violence, holding that the real nature of the universe under God is shown in the suffering love and resurrection of Jesus, and therefore an active non-violent social ethic is necessary for the imitation of Christ, not only for ‘peace churches’ but for all. Moreover, since suffering love is not only the key to the Gospel but also to the universe, this ethic is to be found globally. Yoder's seminal work was The politics of Jesus (1972). He died as a professor at Notre Dame University, having established the Mennonite-Catholic connection that continues with Lederach today and bears fruit in the new field of peace-building. In 1983 he gave these eleven lectures, now published for the first time, to non-Catholics in Warsaw, invited by the Polish Ecumenical Council, the context being the Polish non-violent liberation struggle. Not a full history of non-violence, the lectures cover the modern period in the thought of Leo Tolstoy and his influence on Gandhi and in turn Martin Luther King; a critique of the nature and use of the Just War tradition; an engagement with current conflict theory; the continuity of a strand of non-violent theology within Old Testament Judaism, the teachings of Jesus, and the concept of ‘the powers’ in pre-Constantinian Christianity; and three chapters on twentieth-century Catholic non-violent thought and liberation theology. The whole forms a sustained argument for the non-violent position, and is a useful accessible introduction to Yoder's work.