Didache 1.3-6, 100:

3 What these maxims teach is this: “Bless those who curse you,” and “pray for your enemies.” Moreover, fast “for those who persecute you.” For “what credit is it to you if you love those who love you? Is that not the way the heathen act?” But “you must love those who hate you,” and then you will make no enemies.

4 “Abstain from carnal passions.” If someone strikes you “on the right cheek, turn to him the other too, and you will be perfect.” If someone “forces you to go one mile with him, go along with him for two”; if someone robs you “of your overcoat, give him your suit as well.” If someone deprives you of “your property, do not ask for it back.” (You could not get it back anyway!)

5 “Give to everybody who begs from you, and ask for no return.” For the Father wants his own gifts to be universally shared. Happy is the man who gives as the commandment bids him, for he is guiltless! But alas for the man who receives! If he receives because he is in need, he will be guiltless. But if he is not in need he will have to stand trial why he received and for what purpose. He will be thrown into prison and have his action investigated; and “he will not get out until he has paid back the last cent.”

6 Indeed, there is a further saying that relates to this: “Let your donation sweat in your hands until you know to whom to give it.”

Letter to Diognetus ch. 5, A.D. 100 – 130:

Christians … love all men, and are persecuted by all. They are unknown and condemned; they are put to death, and restored to life.  They are poor, yet make many rich;  they are in lack of all things, and yet abound in all; they are dishonored, and yet in their very dishonor are glorified. They are evil spoken of, and yet are justified; they are reviled, and bless;  they are insulted, and repay the insult with honor; they do good, yet are punished as evil-doers. When punished, they rejoice as if quickened into life. They are assailed by the Jews as foreigners, and are persecuted by the Greeks; yet those who hate them are unable to assign any reason for their hatred.

Tatian, 160:

I do not wish to be a king. I am not anxious to be rich. I decline military command.

St. Justin Martyr, 165 AD:

"For out of Zion shall go forth the law, and the word of the Lord from Jerusalem. And he shall judge among the nations, and shall rebuke many people; and they shall beat their swords into ploughshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more" [Is. 2:3]. And that this did come to pass, we can convince you.

For from Jerusalem men went out into the world, twelve in number and these illiterate, of no ability in speaking; but by the power of God they proclaimed to every race of men that they were sent by Christ to teach to all the word of God. Now we who used to murder one another do not only refrain from making war upon our enemies, but also, that we may not lie nor deceive our examiners, willingly die confessing Christ.

For that saying, "The tongue has sworn but the mind is unsworn" [a justification for lying used in Justin's time], might be imitated by us in this matter. But if the soldiers enrolled by you, who have taken the military oath, prefer their allegiance to their own life, parents, country, and all kindred, though you can offer them nothing incorruptible, it would be truly ridiculous if we, who earnestly long for incorruption, should not endure all things in order to obtain what we desire from him who is able to grant it. (First Apology 39)

We who were filled with war, mutual slaughter, and every wickedness have each, through the whole earth, changed our warlike weapons—our swords into ploughshares and our spears into implements of tillage. In their place, we cultivate godliness, righteousness, philanthropy, faith, and hope, which we have from the Father himself through the One who was crucified. (Dialogue with Trypho 110)

Athenagoras, A Plea for Christians 35 (180AD):

“[People know] that we cannot endure even to see a man put to death, though justly…But we, deeming that to see a man put to death is much the same as killing him, reject such spectacles.  How, then, when we do not even look on, lest we should contract guilt and pollution, can we put people to death? And when we say that those women who use drugs to bring on abortion commit murder, and will have to give an account to God for the abortion, on what principle should we commit murder?”

“We have learned not to return blow for blow, nor to go to law with those who plunder and rob us. Instead, even to those who strike us on one side of the face, we offer the other side also.

Irenaeus: a.d. 180:

The new covenant that brings back peace and the law that gives life have gone forth over the whole earth, as the prophets said: “For out of Zion will go forth the law, and the word of the Lord from Jerusalem; and he will rebuke many people; and they will break down their swords into plowshares, and their spears into pruning hooks, and they will no longer learn to fight”…These people [Christians] formed their swords and war-lances into plowshares,…that is, into instruments used for peaceful purposes. So now, they are unaccustomed to fighting. When they are struck, they offer also the other cheek.

St. Clement of Alexandria, 190-215 AD:

The Church is an army of peace which sheds no blood. In peace, not in war, we are trained.

The Scythians, the Celts, the Iberians, and the Thracians are all warlike races. They are also greatly addicted to intoxication and think that drunkenness is an honorable, happy pursuit to engage in. But we, the people of peace, feast for lawful enjoyment, not to wantonness. We drink sober cups of friendship.

The one instrument of peace is what we employ: the Word alone, by whom we honor God. We no longer use the ancient psaltery, trumpet, timbrel, and flute. For those who are expert in war are scorners of the fear of God were accustomed to make use of them.

Let our seals be either a dove, a fish, or a ship scudding before the wind…If there is anyone fishing, he will remember the apostle, and the children drawn out of the water. We are not to draw an outline of…a sword or a bow, since we follow peace. Nor should we draw an outline of…drinking cups, since we are temperate.

He bids us to “love our enemies, bless them who curse us, and pray for those who despitefully use us.” And he says: “If anyone strikes you on the one cheek, turn to him the other also; and if anyone takes away your coat, do not hinder him from taking your cloak also.”

An enemy must be aided, so that he may not continue as an enemy. For by help, good feeling is compacted and enmity dissolved.

We do not train our women like Amazons to manliness in war, for we wish even the men to be peaceable.

For we are not to delineate the faces of idols, we who are prohibited to cleave to them; nor a sword, nor a bow, since we follow peace. (The Instructor III:11)

Tertullian, c. A.D. 210:

The Christian does no harm even to his foe. (Apology 46)

Origen Against Celsus 3.7 (250AD):

“If a revolution had led to the formation of the [Church], so that it derived its existence in this way from that of the Jews, who were permitted to take up arms in defense of the members of their families, and to slay their enemies, [Jesus] would not have altogether forbidden the putting of men to death; and yet He nowhere teaches that it is right for His own disciples to offer violence to any one, however wicked. For He did not…allow the killing of any individual for any reason. [Instead] it was their fate to be slain as sheep, & on any occasion to resist their persecutors.”

The existence of many kingdoms would have been a hindrance to the spread of the doctrine of Jesus throughout the entire world…This was because of the need for men everywhere to engage in war and fight on behalf of their native country–which was the case before the times of Augustus…How, then, was it possible for the gospel doctrine of peace to prevail throughout the world? For it does not permit men to take vengeance even upon their enemies. It was only possible because, at the coming of Jesus, a milder spirit had been everywhere introduced into the conduct of things.

The statement is false “that in the days of Jesus, others who were Jews rebelled against the Jewish state and became his followers.” For neither Celsus, nor those who think like him, are able to point out any act on the part of Christians that hints of rebellion. In fact, if a revolt had led to the formation of the Christian commonwealth, the Christian Lawgiver would not have altogether forbidden the putting of men to death. So it could not have derived its existence in such a way from the Jews. For they were permitted to take up arms in defense of the members of their families and to slay their enemies. Yet, Christ nowhere teaches that it is right for his own disciples to offer violence to anyone, no matter how wicked. For he did not consider it to be in accord with his laws to allow the killing of any individual whomever. For his laws were derived from a divine source. Indeed, if the Christians truly owed their origin to a rebellion, they would not have adopted laws of so exceedingly mild a character. For their laws do not allow them on any occasion to resist their persecutors, even when it was their fate to be slain as sheep.

Christians were taught not to avenge themselves upon their enemies…They would not have made war (although capable) even if they had received authority to do so. For they have obtained this reward from God: that he has always warred on their behalf. On certain occasions, he has restrained those who rose up against them and desired to destroy them…On special occasions, some have endured death for the sake of Christianity, and those individuals can be easily numbered. However, God has not permitted the whole nation [of Christians] to be exterminated.

To those who inquire of us from where we come, or who is our founder, we reply that we have come agreeably to the counsels of Jesus. We have cut down our hostile, insolent, and wearisome swords into plowshares. We have converted into pruning hooks the spears that were formerly used in war. For we no longer take up “sword against nation,” nor do we “learn war any more.” That is because we have become children of peace for the sake of Jesus, who is our leader.

Celsus [a critic of Christianity] adds…”How could God command the Israelites through Moses to gather wealth, to extend their dominion, to fill the earth, to put their enemies of every age to the sword, and to destroy them utterly?…For, on the other hand, his Son, the man of Nazareth, promulgated laws quite opposed to these. He declared that no one can come to the Father who loves power, riches, or glory. Jesus said that to anyone who has given them one blow, they should offer to receive another, So is it Moses or Jesus who taught falsely? When the Father sent Jesus, did he forget the commands that he had given Moses? Or did he change his mind, condemn his own laws, and send forth a messenger with opposite instructions?…

[In reply to this Origen states,] We would observe that it must be impossible for the legislation of Moses, taken literally, to harmonize with the calling of the Gentiles and with their subjection to the Roman government. On the other hand, it would be impossible for the Jews to preserve their civil economy unchanged if they were to embrace the gospel. For Christians could not slay their enemies. Nor could they condemn those who had broken the law to be burned or stoned, as Moses commands….In the case of the ancient Jews, who had a land and a form of government of their own, to take from them the right of making war upon their enemies, of fighting for their country, of putting to death or otherwise punishing adulterers, murderers, or others who were guilty of similar crimes, would have been to subject them to sudden and utter destruction whenever the enemy fell upon them. For, in that case, their very laws would restrain them and prevent them from resisting the enemy. Yet, that same providence that of old gave the Law, and has now given the gospel of Jesus Christ, has destroyed their city and their temple, not wishing the Jewish state to continue any longer…However, this providence has extended the Christian religion day by day, so that it is now preached everywhere with boldness. And this is in spite of the numerous obstacles that oppose the spread of Christ’s teaching in the world. However, since it was the purpose of God that the nations should receive the benefits of Christ’s teaching, all th edevices of men against Christians have been brought to nothing. For the more that kings, rulers, and peoples have persecuted them everywhere, the more Christians have increased in number and grown in strength.

[Celsus further says,] You surely do not say that if (in compliance with your wish) the Romans were to neglect their customary duties to gods and men, and were to worship the Most High,….that he would come down and fight for them, so that they would not need any other help than his. For this same God…promised of old this and much more to those who served him. Yet, see in what way he has helped the Jews and you! Instead of being masters of the whole world, the Jews are left with not so much as a patch of ground or a home.

[Origen replied,] What would happen if, instead of only a relatively few persons believing (as at the present), the entire empire of Rome believed? They would pray to the Word, who of old said to the Hebrews, when they were pursued by the Egyptians, “The Lord will fight for you, and you will hold your peace.” And if all the Romans united in prayer with one accord, they would be able to put to flight far more enemies than those who were defeated by the prayer of Moses…However, he had made the fulfillment of his promises dependent on certain conditions–namely, that they would observe and live according to his law…But if all the Romans embraced the Christian faith (according to the supposition of Celsus), they would overcome their enemies when they prayed. Or rather, they would not war at all. For they would be guarded by that divine power that promised to save five entire cities for the sake of fifty righteous persons. Men of God are assuredly the salt of the earth. They preserve the order of the world. And society is held together as long as the salt is uncorrupted…When God gives to the Tempter permission to persecute us, then we suffer persecution. And when God wishes us to be free from suffering–even in the middle of a world that hates us–we enjoy a wonderful peace, trusting in the protection of him who said, “Be of good cheer, for I have overcome the world.”

In the next place, Celsus urges us “to help the king with all our might, to labor with him in the maintenance of justice, and to fight for him. Or if he demands it, to fight under him or lead an army along with him.” To this, our answer is that we do give help to kings when needed. But this is, so to speak, a divine help, “putting on the whole armor of God.” And we do this in obedience to the commandment of the apostle: “I exhort, therefore that first of all, supplications, prayers, intercessions, and thanksgiving be made for all men; for kings, and for all who are in authority.” So the more anyone excels in godliness, the more effective the help is that he renders to kings. This is a greater help than what is given by soldiers who go forth to fight and kill as many of the enemy as they can. And to those enemies of our faith who demand us to bear arms for the commonwealth and to slay men, we reply: “Do not those who are priests at certain shrines…keep their hands free from blood, so that they may offer the appointed sacrifices to your gods with unstained hands that are free from human blood? Even when war is upon you, you never enlist the priests and ministers of God, keeping their haands pure. For they wrestle in prayers to God on behalf of those who are fighting in a righteous cause, and for the king who reigns righteously. They pray that whatever is opposed to those who act righteously may be destroyed.

Our prayers defeat all demons who stir up war. Those demons also lead persons to violate their oaths and to disturb the peace. Accordingly, in this way, we are much more helpful to the kings than those who go into the field to fight for them. And we do take our part in public affairs when we join self-denying exercises to our righteous prayers and meditations, which teach us to despise pleasures and not to be led away by them. So none fight better for the king than we do. Indeed, we do not fight under him even if he demands it. Yet, we fight on his behalf, forming a special army–an army of godliness–by offering our prayers to God. And if Celsus would have us “lead armies in defense our country,” let him know that we do this too. And we do not do it for the purpose of being seen by men or for vainglory. For in secret, and in our own hearts, our prayers ascend on behalf of our fellow-citizens, as from priests. And Christians are benefactors of their country more than others. For they train up citizens and inculcate piety to the Supreme Being. And they promote to a divine and heavenly city those whose lives in the smallest cities have been good and worthy.

St. Cyprian of Carthage, 250-60:

The whole world is wet with mutual blood, and murder, which in the case of an individual is admitted to be a crime, yet is called a virtue when it is committed wholesale. Impunity is claimed for the wicked deeds, not on the plea that they are guiltless, but because the cruelty is perpetrated on a grand scale. (Letters of Cyprian I:6)

Christians do not attack their assailants in return, for it is not lawful for the innocent to kill even the guilty.

The hand must not be spotted with the sword and blood-not after the Eucharist is carried in it.

Arnobius: a.d. 305:

You allege that those wars of which you speak were sparked because of hatred of our religion. However, it would not be difficult to prove that (after the name of Christ was heard in the world), wars were not increased. In fact, they actually diminished in great measure by the restraining of furious passions. A numerous band of men as we are, we have learned from his teaching and his laws that evil should not be repaid with evil. Rather, it is better to suffer wrong than to inflict it. We would rather shed our own blood than stain our hands and our conscience with that of another. As a result, an ungrateful world is now enjoying–and for a long period has enjoyed–a benefit from Christ. For by his means, the rage of savage ferocity has been softened and has begun to withhold hostile hands from the blood of a fellow creature. In fact, if all men without exception…would lend an ear for a while to his salutary and peaceful rules,…the whole world would be living in the most peaceful tranquility. The world would have turned the use of steel into more peaceful uses and would unite together in blessed harmony, maintaining inviolate the sanctity of treaties.

Lactantius, 300-320:

For when God forbids us to kill, He not only prohibits us from open violence, which is not even allowed by the public laws, but He warns us against doing things which are considered lawful among men. Thus it will not be lawful for a just man to engage in warfare, since the kind of fighting appropriate to him is to do justice.

When the worship of God was taken away, men lost the knowledge of good and evil… They then began to fight with one another, to plot, and to achieve glory for themselves from the shedding of human blood.

If only God were worshiped, there would not be dissensions and wars. For men would know that they are the sons of one God.

Why would [the just man] carry on war and mix himself with the passions of others when his mind is engaged in perpetual peace with men? Would he be delighted with foreign merchandise or with human blood–he who does not know how to seek gain? For the Christian is satisfied with his standard of living. He considers it unlawful not only to commit slaughter himself, but also to be present with those who do it.

If desire is restrained, no one will use violence by land or by sea. No one will lead an army to carry off and lay waste the property of others… For what are the interests of our country, but the detriments of another state or nation? To extend the boundaries that are violently taken from others, to increase the power of the state, to improve the revenues–all of these things are not virtues. Rather, they are the overthrowing of virtues.

How can a man be just who hates, who despoils, who puts to death? Yet, those who strive to be serviceable to their country do all these things…When they speak of the “duties” relating to warfare, their speech pertains neither to justice nor to true virtue.

The Stoics say that the emotion of anger is the whetstone of virtue. As though no one could fight bravely against enemies unless he were excited by anger. By this, they plainly show that they neither know what virtue is, nor why God gave anger to man. If it were given to us for the purpose of using it to slay men, then what creature can be considered more savage than man? Who resembles the wild beasts more than the creature whom God formed for communion and innocence?

Therefore, it is not befitting that those who strive to keep to the path of justice should be companions and sharers in this public homicide. For when God forbids us to kill, he prohibits more than the open violence that is not even allowed by the public laws. He also warns us against doing those things that are considered lawful among men. For that reason, it will not be lawful for a just man to engage in warfare, since his warfare is justice itself. Nor is it lawful for him to accuse anyone of a capital charge. For it makes no difference whether you put a man to death by word, or by the sword instead. That is because it is the act of putting to death itself that is prohibited. Therefore, with regard to this commandment of God, there should be no exception at all. Rather, it is always lawful to put a man to death, whom God willed to be a sacred creature.

It is not right that a worshiper of God should be injured by another worshiper of God.

Disputation of Archelaus and Manes: a.d. 320

Those soldiers were filled with wonder and admiration at the grandeur of the man’s piety and generosity and were struck with amazement. They felt the force of this example of pity. As a result, very many of them were added to the faith of our Lord Jesus Christ and threw off the belt of military service.

St. Martin of Tours, 397:

I am a soldier of Christ. It is not permissible for me to fight.

The Apostolic Tradition of Hippolytus 215AD.

16.7 If someone is a gladiator, or one who teaches those among the gladiators how to fight, or a hunter who is in the wild beast shows in the arena, or a public official who is concerned with gladiator shows, either he shall cease, or he shall be rejected.

9 A military man in authority must not execute men. If he is ordered, he must not carry it out. Nor must he take military oath. If he refuses, he shall be rejected.

10 If someone is a military governor (has the authority of swords), or the ruler of a city who wears the purple, he shall cease or he shall be rejected.

Council of Nicaea, 325AD:

If a military man wanted to convert, he would first have to do penitence for ten years, which was even more than the penitence of seven years required for someone who denied Christ under persecution.

Council of Chalcedon, 7^th Canon:

“shall not accept military service nor any secular dignity,” and if they “do not repent… they shall be anathematized”.