The last chapter of William Shannon's guide to deepening your prayer life, Seeking the Face of God, is entitled, "Guigo's Ladder and Gandhi's Satyagraha." There, he traces the development of the "Just-War Doctrine," to immediately after the rule of Constantine, when Christianity had become the religion of the Empire, so government and the gospel were intertwined.
He begins with the observation that many Christians who have been converted to nonviolence have been brought to it through a man who was not Christian, Gandhi, who, ironically enough, first learned about nonviolence from Christian sources and his reading of the New Testament.
"It is surely a sign of the unity of so many deep religious perceptions that it was Jesus who taught Gandhi how to read the Bhagavad Gita! For a goodly number of Christians the journey has been in the opposite direction: they found nonviolence in Gandhi before they were able to find it in their own Christian Scriptures. Gandhi taught them how to read the Sermon on the Mount!"