“To begin with the real ground of the military crown, I think we must first inquire whether warfare is proper at all for Christians. What sense is there in discussing the merely accidental, when that on which it rests is to be condemned? Do we believe it lawful for a human oath to be superadded to one divine, for a man to come under promise to another master after Christ, and to abjure father, mother, and all nearest kinsfolk, whom even the law has commanded us to honour and love next to God Himself, to whom the gospel, too, holding them only of less account than Christ, has in like manner rendered honour? Shall it be held lawful to make an occupation of the sword, when the Lord proclaims that he who uses the sword shall perish by the sword? And shall the son of peace take part in the battle when it does not become him even to sue at law? And shall he apply the chain, and the prison, and the torture, and the punishment, who is not the avenger even of his own wrongs? Shall he, forsooth, either keep watch-service for others more than for Christ, or shall he do it on the Lord’s day, when he does not even do it for Christ Himself? And shall he keep guard before the temples which he has renounced? And shall he take a meal where the apostle has forbidden him? And shall he diligently protect by night those whom in the day-time he has put to flight by his exorcisms, leaning and resting on the spear the while with which Christ’s side was pierced? Shall he carry a flag, too, hostile to Christ?…Is the laurel of the triumph made of leaves, or of corpses? Is it adorned with ribbons, or with tombs? Is it bedewed with ointments, or with the tears of wives and mothers? It may be of some Christians too; for Christ is also among the barbarians.”
Tertullian is arguing in support of a Christian soldier who refused to put on the laurel crown given to his company after a military victory. Wearing the laurel crown had some connotations of devotion to the civic deities of the Empire and was against the practice of the North African Christian community. The crown itself, however, is not the major issue in Tertullian’s mind as he is writing. He is more concerned with the unity of the church’s witness to the surrounding culture than with buttressing any legalism. At least some of the Christians of Carthage were beginning to question whether it was really a grave matter to participate in some aspects of Roman civic religion. Tertullian’s answer refuses to honor the legitimacy of the question about precisely where to draw the line of idolatry. Not only does he question the crown, he questions the actions that lead to being rewarded and recognized as a servant of the Empire. In this context, he offers a powerful argument against Christian participation in the military—Christ is also among the barbarians!
As much as Tertullian wants to distinguish “Athens” and “Jerusalem,” it isn’t because he’s consigned Athens to eternal destruction. As he writes in polished Latin, drawing on the best of the philosophical and rhetorical traditions of his day, Tertullian is concerned that Christ should be honored everywhere that he may be found—and not at the point of the world’s sword.
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Excerpted from De Corona, chapters 11 and 12.
eric daryl meyer 
I think it is misleading to post Tertullian without clearly stating that his views became extreme after he turned away from the catholic church. Even in this treatise Tertullian mentions that other Christians were serving along with this soldier. Of course, Tertullian completely discounts the faith of these men, saying that only the young man who refused to wear his capulet was truly a Christian.
The more recent archaeological discoveries clearly show that Christians served in the Roman military even prior to the account recorded by Tertullian under Marcus Aurelius, the famous story of the Thundering Legion. One of several Christian gravestones uncovered was of a soldier dated 201 AD. Also unearthed a chapel within a military fortress in Meggido dated to the early third century.
While the discussion of the peace gospel included in the sayings of Jesus is certainly a theological concern and worthy of consideration for supporting a pacifist stance, bringing the early church into the discussion is a matter of history. The historical data, even prior to the recent discoveries, clearly indicates that primitive/early Christianity did not hold to a pacifist stance. Tertullian did after leaving the church, but other negative comments by church fathers are almost certainly driven by the idolatry commonly practiced in the Roman military…yet the evidence clearly shows that Christians served in the Roman military at least as early as the mid second century. Many scholars think the evidence points to Christian involvement from a very early date.