True Christians Fight Sin, Not War
Perhaps there are two dozen or more questions that accompany this statement, but all of them can be answered in one reply, a simple teaching right from Jesus' own mouth: "Love your enemies".
Historically the Early Church was non-resistant, meaning that they did not participate in warfare through military service, or political office. In fact they took Jesus' teachings to love your enemies so literally they taught that a Christian was commanded to actually turn the other cheek when someone slapped him. Have you ever wondered why the Early Church never retaliated when they were persecuted by the Roman Government? This is why.
Around the year 350 all of this changed when the Roman Emperor Constantine embraced Christianity, and began to influence the Church's decision-making processes. Until the year 350 the Early Church was the persecuted, however when Constantine was "converted" he produced an edict that effectively made the Church the persecutors. Constantine's new law declared that anyone dubbed as a heretic by the church majority was to be killed. So why was this such a turning point in Early Church history? Because it marked a point in the road where the Early Church departed from Jesus' simple teachings in Mathew 5, 6 and 7. The teachings to love your enemies; teachings that the Early Church had formerly upheld even in the fiercest persecutions. However, with the influence of Constantine's new edict to kill heretics, the Church took a sharp turn from loving their enemies as Jesus did, to killing their enemies as Pilate did.
When we continue to look at Early Church history we can see another exit ramp that lead the Early Church away from Jesus' teaching on non-resistance. The driver that took the early church down this new road was a theologian named Augustine of Hippo. Before Augustine was converted to Christianity he was part of the Manichean faith, a religion that taught an extreme form of dualism - the idea that good and evil are equal powers. As a result of this teaching the Manicheans believed that the body and spirit were two separate beings independent of one another. Why mention this? Well, because it affected the way Augustine understood and taught Jesus' teachings.
Augustine wrote: "It could be supposed that God did not authorize warfare because of what the Lord Jesus Christ taught, saying: "I say unto you that you resist not evil. But if anyone strikes you upon the right cheek turn to him the left also". However, the answer here is that what is required is not a bodily action, but an inward disposition".... "The Lord requires patience when He says: "if anyone strikes you on the right cheek turn to him the other also." This may be in the inward disposition, although it is not exhibited in bodily action or in words". (From Augustine ch.75 The Ante-Nicene Fathers)
It was as if Augustine was saying "its perfectly acceptable to kill your enemy, as long as you love him while you are doing it". But how can you love someone and hold a gun to their head? How can you separate your bodily actions from your "inward disposition"?
What Augustine taught was definitely a sharp veering off of the narrow road and a turn going in a completely different direction from what the Church had believed and practiced historically. How do we know this? Because we can read what the early church Christians believed, and how they practiced Jesus' teachings. One of the first Christian writings that historians are aware of is an apology written by a Christian named Justin, it is dated at around 150.
Justin wrote to the Roman government who persecuted the Christians: "We used to hate and destroy one another, and refused to associate with people of another race or country. Now, because of Christ we live together with such people, and pray for our enemies." (Justin's first apology Chapter 11)
Another early church writer named Cyprian wrote: "We are scattered all over the world with the bloody horror of camps (military outposts). The whole world is wet with mutual blood. And murder - which is admitted to be a crime in the case of an individual - is called virtue when it is committed wholesale. Impunity is claimed for the (military's) wicked deeds, not because they are guiltless - but because the cruelty is perpetuated on a grand scale!" - Cyprian (c.250) vol. 5 pp. 277 of the Ante-Nicene Fathers
An early church Christian who lived in the early 300's named Lactantius wrote: "If we all derive our origin from one man, whom God created, we are plainly all of one family. Therefore it must be considered an abomination to hate another human, no matter how guilty he may be. For this reason God has decreed that we should hate no one, but that we should eliminate hatred. So we can comfort our enemies by reminding them of our mutual relationship. For if we have all been given life by the same God then what else are we but brothers? ... Because we are all brothers God teaches us never to do evil to one another but only good - giving aid to those who are oppressed, and experiencing hardship, and giving food to the hungry." - Lactantius (Divine Institutes bk. 6 ch 10.)
Nearly all of the Early church writers who taught non-resistance backed up their beliefs with martyrdom, proving that they were willing to die before they would take another persons life. However for Augustine the story was completely different. Augustine framed what is commonly referred to as the "Just War Doctrine" - a teaching that attempts to justify war if certain criteria are met. Augustine's Just War Doctrine went smack against what Jesus said in Mathew 5: "You have heard that it has been said: an eye for an eye and a tooth for a tooth, but I tell you do not resist an evil person. If someone slaps you on the right cheek turn to him the other also".
Unlike the bold Christians that went before him, Augustine never gave his life for the faith, and his theology doesn't seem to suggest he was willing to either. Perhaps he was unwilling because he saw that Christ's teachings were going to require more than he was willing to give. Perhaps like many others, Augustine didn't want to follow Jesus' teachings and turn the other cheek, so he simply created a theology that got him out of it. Consequently it gave others a cop-out as well.
With Augustine's Just War doctrine, the Early Church had a new road map that would eventually lead it toward events such as the British Crusades, the European Inquisitions, and many other atrocities led by the Spanish Catholic Conquistadors. These events would consequently cause the world to question why the christianity that speaks so much about love and forgiveness won't do the same...
Is all of this history enough to convince you that a Christian ought to love his enemies? Perhaps not, but what are you going to do with what Jesus said: "Love your enemies." And what will you do standing before the Lord when He asks "I loved you when you were my enemy, why didn't you do the same for yours?"