To start with the first point, it was an ancient heresy of the Manicheans to argue that war was by nature unlawful, and therefore they accused Moses, Joshua, David, and other Fathers of the Old Testament, who waged wars, of impiety, as blessed Augustine reports in Contra Faustum, book 22, chapters 74ff.123 Some people brought up the same heresy in our time, and especially Erasmus who in various places, but especially in Annotationes ad capitulos III et XXII Lucae, argued at length that war was one of the evils that God tolerated and permitted to the ancient Jews, but that war was forbidden to the Christians by Christ and the apostles.124
Also Cornelius Agrippa in De vanitate scientiarum, chapter 79, affirms that the practice of war was prohibited by Christ. So did Johann Wild in book 4 of his commentaries on Matthew, with an explanation of the passage in chapter 26: “All they that take the sword shall perish with the sword.” The Anabaptists teach the same, as Melanchthon attests in his Loci, chapter on the magistrate. Alfonso de Castro attributed the same doctrine to Oecolampadius under the entry “war,” which seems surprising to me, since Zwingli, his associate, approved of war so much that he died fighting in battle; and Calvin in book 4 of the Institutiones, chapter 20. Melanchthon, as quoted before, and other heretics of the time likewise teach in word and deed that war should be waged.
By contrast, just as the whole Church always taught in words and examples, we say that war by nature is not unlawful, and waging war is allowed not only to the Jews but also to the Christians, provided that the conditions which we will later discuss are fulfilled. This is proved by the evidence of Scripture, in Judges 3: “Now these are the nations which the Lord left, to prove Israel by them, even as many of Israel as had not known all the wars of Canaan; Only that the generations of the children of Israel might know, to teach them war, at the least such as before knew nothing thereof.”125 These words not only show God’s permission but God’s absolute will. Likewise in 1 Kings 15: “Thus saith the Lord of hosts, I remember that which Amalek did to Israel, how he laid wait for him in the way, when he came up from Egypt. Now go and smite Amalek, and utterly destroy all that they have, and spare them not, etc.”126 Here also we see not a permission but a command, and the Old Testament is full of similar instances. The same in Luke 3: “And the soldiers likewise demanded of him, saying, And what shall we do? And he said unto them, Do violence to no man, neither accuse any falsely; and be content with your wages.”127 The Anabaptists, according to Melanchthon, say that John allowed the Jews war because they were imperfect and that Christ taught something entirely different.
On the contrary, since John was preparing the path for the Lord, he cannot have allowed what Christ was soon to remove. Also, the Jews could not make use of that permission, since Christ would come the same year and prohibit war, as they would have it. Moreover, men might have suspected that Christ and John did not agree with each other, which would have been truly absurd. Erasmus replies otherwise, that these commands are given to the soldiers not so that they might live well following them, but so that they might live less badly, which seems also to be Theophylactus’s interpretation.
But it is otherwise, for John had said before: “Bring forth therefore fruits worthy of repentance,” and “Every tree therefore which bringeth not forth good fruit is hewn down, and cast into the fire.”128 As a consequence, the repenting publicans and soldiers asked what was the good fruit they should bring forth. So either John deceived them, or soldiers can attain salvation if they fulfill what John commanded them.
Regarding Theophylactus, I say two things. First, he does not say that war is evil, but only that John exhorted the people who were innocent to do good, that is, to share their goods with the others, but he exhorted the publicans and soldiers, who were incapable of such perfection and could not do works of supererogation, to desist from evil. In fact, Theophylactus thought that for somebody who has two coats to give one to him who has none was a work of counsel and supererogation; otherwise he would not call the people innocent to whom he was speaking, and neither would he distinguish this act as good rather than evil, for if it is a command not to keep two coats, keeping them will be an evil act.
Second, Theophylactus does not correctly interpret this passage, for he calls the people innocent whom John calls a “generation of vipers” and says to “bring forth therefore fruits worthy of repentance.”129 Moreover, keeping two coats means keeping what is superfluous, as Jerome says in question 1, Ad Hedibiam, and it is a sin to keep what is superfluous. Furthermore, in Matthew 22 our Lord taught that the tribute to Caesar must be paid, and certainly no tribute is owed to kings for any other purpose but to sustain the army in defense of the commonwealth, which the apostle explains in Romans 13: “For this cause pay ye tribute also: for they are God’s ministers, attending continually upon this very thing,”130 that is, to punish with their sword those who disturb the public peace, for before he had said: “For he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil.”131
Second, it is proved by the examples of the saints who waged wars, for if war were evil, certainly it would not be waged by saints. In the Old Testament we read that Abraham, Moses, Joshua, Gideon, Samson, David, Josiah, and the Maccabees waged war with much praise. In the New Testament, Matthew 8, when the centurion said to Christ, “For I am a man under authority, having soldiers under me: and I say to this man, Go, and he goeth; and to another, Come, and he cometh, etc.,”132 the Lord praised him for his faith and did not command him to leave the army. In Acts 10, the same centurion, Cornelius, is called “a just man and one that feareth God”133 so much so that he deserved to see an angel, and afterward, after being taught the path to salvation by St. Peter, he was not told to leave the army.
Subsequently, after Christ’s ascension to heaven, there were always Christians in the army, even under pagan princes, some of them truly holy and beloved by God, as Tertullian teaches in Apologeticus, chapter 5, where he reports a great miracle performed by Christian soldiers when they were fighting under Marcus Aurelius in Germany. They would certainly not have been in the army if that was evil, and even if they were, they would not have been so beloved by God that they were even able to perform miracles. See also Eusebius, Historia, book 8, chapter 4, and book 9, chapter 10 [9]. Basil also teaches in Oratio in laudem SS. 40 Martyrum that there were many holy men in the army of pagan emperors, and likewise Gregory of Nazianzus in his first oration In Julianum [4], in the second part. Finally, it is established that Constantine, Theodosius, Valentinian, Charlemagne, St. Louis the king of France, St. Maurice with his legion of Thebans, and many other Christian saints waged wars, and the holy bishops never blamed them; indeed, Theodosius asked the Abbot John for advice on the outcome of the war, as Augustine reports in book 5 of De civitate Dei, chapter 26.
Third, it is proved because God always assists just wars, which of course He would not do if war were unlawful, for evil deeds may be allowed, but support to do evil deeds can never be given. In Genesis 14 Melchizedek said to Abram after he defeated four kings with only 318 servants, “Blessed be the most high God, which hath delivered thine enemies into thy hand.”134 In Exodus 17, answering the prayers of Moses, God gave victory to the Hebrews against Amalek; in Joshua 10, when Joshua was fighting, the sun stood still and God made great stones fall from heaven as rain and with the hailstorm of stones He killed more people than the sons of Israel with spears and swords. In 2 Maccabees 10135 angels appearing as knights fought with the Maccabees, and at chapter 15 we read that God gives victory to the worthy ones not because of the strength of the armies but as He wishes.
Eusebius in De vita Constantini and in book 9 of Historia, chapter 9, attests that Constantine won battles with the help of God and through clearly proved miracles; Theodoretus in Historia, book 5, chapter 5, attests that the apostles St. John and St. Philip fought openly with Theodosius against his enemies; Socrates in book 7, chapter 18, writes that angels fought for the younger Theodosius against the Saracens; on Clodoveus, see Gregory of Tours, book 2 of the Historia