Roland Bainton's Christian Attitudes Toward War and Peace is perhaps one of the most important and well-documented accounts of the various Christian "positions" toward participation in war, and offers a candid, even if dated (1961) account of the stakes of Christian peace-making.Here, you'll find a critical appraisal of the three fundamental Christian perspectives: Pacifism, just war, and the crusade. And as a church historian, Bainton carefully connects those positions to early Christian faith.
Earliest Christians had an essential aversion toward taking life. And thus were committed to a pacifism that was Christologically grounded. Discipleship to Jesus, to their mind, made participation in war absolutely verboten. "From the end of the New Testament period to the decade A.D. 160-170 there is no evidence whatever of Christians in the army" (pp 67-68).
But with the rise of the just war position, theologians like Ambrose and later Augustine, connected Christian participation in war with the restoration of justice and the maintenance of peace for one's neighbors. If the motive was the love of neighbor, and the violence was overseen by the authority of a responsible ruler, and its conduct in accord with principles of fairness and justice, then Christians should always mournfully engage in any violence. This has been the dominant position, according to Bainton, but Christians have always struggled to articulate what justice and kindness are in connection to love of neighbor. Which neighbor? Whose justice?
By contrast, the crusade position, according to Bainton, was always a perversion of the principles of the previous two perspectives, and is an "outlier" in the theological position of Christian history.
Bainton's is an important historical account that, even though dated, demands working through -- particularly in terms of the American blood-lust.