Ronald J. Sider
The Early Church on War and Killing
Iosif and Shean both fail to appreciate the full significance of Origen's insistence, in Contra Celsum, that Christians should not join the Roman army. Origen was probably the most widely read Christian writer of the first half of the 3rd century. A friend and patron of Origen paid for more than a dozen people to write and recopy his flood of writings—contributing greatly to Origen's becoming one of the best-known Christian thinkers of the first half of the 3rd century. As we've already noted, in Contra Celsum Origen refutes the pagan Celsus' charge that if all Romans followed the Christian example of rejecting public office and military service, the Roman Empire would collapse.
Origen's response, in the middle of the 3rd century, was to simply agree with Celsus that Christians do not (and should not) kill or join the army—and then to explain why that is not a problem. In fact, he claims that if all Romans became Christians, war would cease (Contra Celsum, 8.70). If the argument of Shean and Iosif were correct—that most Christians had no problem with military service and that large numbers were serving in the Roman army—then Origen's obvious response would have been to correct Celsus' view that Christians reject military service. But Origen does nothing of the sort. Instead, he matter-of-factly accepts as accurate Celsus' view.
Iosif uses one passage in Clement of Alexandria's Exhortation to argue that this leader of the famous Christian school in Alexandria in the early 3rd century saw no problem with Christians in the military. Clement says: "Practice farming, we say, if you are a farmer, but while you till your fields, know God. Sail the sea, you who are devoted to navigation, yet call the whilst on the heavenly Pilot. Has knowledge taken hold of you while engaged in military service? Listen to the commander, who orders what is right." Iosif claims that Clement is advising the soldier who becomes a Christian to obey his military commander, thus showing that Clement saw no problem with Christians in the army. But there are two flaws in this interpretation. Clement explicitly tells the farmer and sailor who are Christians to continue as they are. But in the third case, that of the soldier who becomes a Christian, Clement does not say to continue as a soldier. Instead, he says obey the commander. Who is the commander? In the previous two cases (farmer and sailor), Clement ends the section with a command to focus on God. It is therefore likely that Clement does the same in the case of the soldier. The commander who is to be listened to is therefore probably Christ. In another text, Clement speaks of Christ as the general who guides his soldiers. We should probably understand this passage along the same lines as The Apostolic Tradition, which says that a soldier who seeks to prepare for baptism must be told not to kill. It is true that Clement says very little about military service. But a number of passages stress the peaceful nature of Christians. And there is no text in Clement that says it is legitimate for Christians to kill or join the army.
One final argument of Shean (and many other modern writers) merits special consideration. Shean points out that the Roman army had enormous power in 3rd- and 4th-century Roman society, even deposing emperors it disliked. Even the strongest Roman emperors had to take account of the thinking of their soldiers. Constantine would not have placed Christian symbols on the shields of his soldiers before the crucial battle at Milvian Bridge in 312 if there had not been a significant number of Christian soldiers in his army. The fact that Christians quickly embraced Constantine, the military conqueror, and rejoiced in his military victories suggests, it is claimed, that opposition to Christians being soldiers had not been widespread in Christian circles.
Several things are important here. First, it is certainly clear from a variety of sources that a growing number of Christians were serving in the Roman army by the late 3rd century. By the first decade of the 4th century, the number of Christian soldiers was substantial.