Interpreting the faith in each new cultural context Successive generations of Christian leaders have set out their advisory thinking on how Christians should respond to human violence and war. In stressing opposition to all forms of violence, the need to follow the example of Jesus is fundamental. In permitting the use of violence in certain prescribed circumstances, it reflects the tradition of reasoned exposition and application of the faith such as was demonstrated by Paul, true to his own Jewish Rabbinic inheritance, and now sometimes characterised as ‘casuistic’.
Pacifists The model of Jesus is all determinative. Not only is murder wrong, but so is the harbouring of murderous thoughts. If provoked, ‘turn the other cheek’. Jesus could have resisted arrest, but he did not. He allowed himself to be killed. The message is plain: avoid engaging in all forms of violence. Throughout the subsequent centuries, there has been continuous evidence of Christians following this example:
· avoidance of service in the Roman army (this was common until Constantine, that is when as Emperor he became Christian)
· non-resistance against those making martyrs of them as in the imperial arena (some even rushed to get themselves killed)
· commitment to a stance of humility in expression of a monastic vow, or the ruling of canon law banning clergy and bishops from engaging in war
· followers of Menno Simons – as Mennonites in both Europe and USA 
· George Fox and the Quakers: refusing weapons in self-defence, but taking the risk of bandaging wounds even in the midst of war.
Some are more rigorously absolutist than others in their interpretation of degrees of association with violence (eg police work). 
Just Warriors Although some Christians in the early centuries refused military service especially when it required treating the Roman Emperor as God, others did serve. Once the Emperor Constantine himself became a Christian in 312AD, any distancing between the public life of a soldier and that of the professing Christian largely ceased. Almost immediately, every Roman soldier carrying a shield had emblazoned on it the cross of Christ. Church leaders successively over the centuries articulated the view that war in certain circumstances was justified, provided it was entered into with the right intent and carried out with due propriety. The succession of theologians teaching this includes Ambrose, Augustine, Gratian, Aquinas, Vittoria, and Grotius. These conventions were very fully articulated within the framework of Christian belief.
"No act is more essentially Christlike than the deliverance of the oppressed. Even if in a particular case the threatened party would be willing in the name of Christ to submit to the injury, it is no whit less my duty to prevent the wrong being done—if possible by persuasion, if not by force. The knight-errant riding the
world in search of distressed damsels to succour is as good a Christian as the Quaker literally turning the
other cheek. ' If possible by persuasion, if not by force. ' " B H Streeter War. This war and the Sermon on the Mount (1915) https://archive.org/details/warthiswarsermon00strerich/page/n4/mode/2up
International law, not Christian v Secular, but both Christian and Secular. Just as their origins drew on sources outside that frame, so their featuring widely in contemporary international law and debate does not depend on the authority of the churches. The key bridging figure in this position is the Dutch Protestant scholar Hugo Grotius who published a treatise in three volumes on The Law of War and Peace in 1625. In his Introduction, he makes clear the rootedness of his own convictions and judgements in the Christian faith, but he uses the phrase ‘etsi deus non daretur’, meaning ‘even if  God were not taken as a given’. (Prologomena 11) Though he immediately repudiates such a position as in his view both wicked and unreasonable, he asserts the validity of international law as potentially independent of religious belief.
On this basis, there is Christian theological legitimation for the continuation of church oriented thinking about how to guarantee justice in society with the minimum use of force and for the shared development of such thinking with people who are not themselves Christian. Thus, in the nineteenth and twentieth centuries, relevant rules were carefully constructed. These pertained to weapon usage, in the St Petersburg Declaration of 1868 and the Hague Conventions of 1899 and 1907. And, likewise pertaining to the personal welfare of participants and bystanders, in the Genevan Conventions of 1864 (treatment of the wounded in field armies), 1906 (treatment of the sick). This was the predominant position of the European churches in 1914.