Complex sentence: He was a prominent member of the Fifth Monarchy Men who saw the overthrow of Charles I as a divine sign of the second coming of Jesus and the establishment of the millennium a thousand years of Christ's rule on earth.
Split into simpler sentences: He was a prominent member of the Fifth Monarchy Men. Who saw the overthrow of Charles I as a divine sign of the second coming of Jesus and the establishment of a thousand years of Christ's rule on earth.