From the very beginning, Christians had always renounced war, violence, and killing of every sort. The writings of the early Christians make this clear:
"We who formerly murdered one another now refrain from making war even upon our enemies" —Justin Martyr
"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." —Athenagoras
"The Christian does no harm even to his enemy." —Tertullian
"God puts His prohibition on every sort of man-killing by that one inclusive commandment: 'You shall not kill.' " —Tertullian
"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 anymore.' That is because we have become children of peace for the sake of Jesus, who is our Leader." —Origen
"Christians do not attack their assailants in return, for it is not lawful for the innocent to kill even the guilty." —Cyprian
Many Christians today spout off about "self-defense," trying to differentiate between "persecution for their faith" and "being assailed in general." What does Scripture teach? What did Jesus say? You profess to be a Christian and yet oppose the very words of your Master. Surely you can see the irony and hypocrisy.
It is an interesting fact that Augustine, Luther, and Calvin repudiated several of Jesus' teachings, and willfully contradicted Him, saying it was perfectly fine for Christians to go to war and commit violence as long as they did so with "love" in their heart. Both Luther and Calvin set themselves up as the Pope of their own religious sects and committed the same atrocities that the Roman Catholics had committed in the name of "God." Many professing Christians today have embraced this same unbiblical mentality, especially professing Christians in the United States. American "Christianity" is a joke! Pride and self-preservation are elevated in today's professing Christians, while the Christians of the first three centuries were humble and counted their lives as nothing. There is quite the stark contrast between the early Christians and today's professing "Christians."
Letter to Diognetus, A.D. 80 - 200
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. (ch. 5)Justin Martyr, c. A.D. 150
"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.D. 177
For when they know that we cannot endure even to see a man put to death, though justly; who of them can accuse us of murder or cannibalism? Who does not reckon among the things of greatest interest the contests of gladiators and wild beasts, especially those which are given by you? But we, deeming that to see a man put to death is much the same as killing him, have abjured such spectacles. How, then, when we do not even watch, 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? (A Plea for the Christians 35)Clement of Alexandria, c. A.D. 190
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)Hippolytus, c. A.D. 225
They will inquire concerning the works and occupations of those are who are brought forward for instruction. If someone is a pimp who supports prostitutes, he shall cease or shall be rejected. If someone is a sculptor or a painter, let them be taught not to make idols. Either let them cease or let them be rejected. If someone is an actor or does shows in the theater, either he shall cease or he shall be rejected. If someone teaches children (worldly knowledge), it is good that he cease. But if he has no (other) trade, let him be permitted. A charioteer, likewise, or one who takes part in the games, or one who goes to the games, he shall cease or he shall be rejected. 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. If someone is a priest of idols, or an attendant of idols, he shall cease or he shall be rejected. 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. If someone is a military governor, or the ruler of a city who wears the purple, he shall cease or he shall be rejected. The catechumen or faithful who wants to become a soldier is to be rejected, for he has despised God. The prostitute, the wanton man, the one who castrates himself, or one who does that which may not be mentioned, are to be rejected, for they are impure. A magus shall not even be brought forward for consideration. An enchanter, or astrologer, or diviner, or interpreter of dreams, or a charlatan, or one who makes amulets, either they shall cease or they shall be rejected. If someone's concubine is a slave, as long as she has raised her children and has clung only to him, let her hear. Otherwise, she shall be rejected. The man who has a concubine must cease and take a wife according to the law. If he will not, he shall be rejected.(Apostolic Tradition 15:6-7; 16:1-16)Origen, c. AD 225
Who among the believers does not know the words in Isaiah? "In the last days the mountain of the Lord shall be revealed, and the house of the Lord on the top of the mountains, and it shall be exalted above the hills. All nations shall come to it. Many people shall go and say, 'Come, and let us go up to the mountain of the Lord, to the house of the God of Jacob, and he will teach us his way, and we will walk in it." For out of Zion shall go forth a law, and a word of the Lord from Jerusalem. He shall judge among the nations, and shall rebuke many people. 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 [Isa. 1:2-5]. (Letter from Origen to Africanus 15) [The early Christians used Isaiah 1:2-5 so regularly that every Christian was familiar with it, believing this passage to be fulfilled by Jesus and His apostles who brought the Word of the Lord from Jerusalem to the entire world, creating a kingdom that lived in peace and refused warfare.Cyprian, c. A.D. 250
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)