Opinion by Candida Moss and Joel Baden, special to CNN

(CNN) – The Air Force has reversed course again and will allow an atheist airman to omit the phrase "so help me God” from its oath, the military branch said Wednesday.

“We are making the appropriate adjustments to ensure our Airmen's rights are protected,” Secretary of the Air Force Deborah Lee James said.

Earlier, the Air Force said the unnamed airman would not be allowed to re-enlist unless he recited the entire oath, including the disputed "God" section.

It was the latest religious controversy in the heavily Christian Air Force, but this particular issue has ancient and somewhat surprising roots: In the early days of Christianity, it was Christians who refused to swear by powers they didn’t believe in.

The oath was written into law in 1956 and, like the Pledge of Allegiance, did not originally include any reference to God. The final sentence came into the text in 1962, just eight years after “under God” was added to the Pledge of Allegiance.

Even then, however, it was not an absolute requirement in the Air Force: Official policy had stated that “Airmen may omit the words ‘so help me God,’ if desired for personal reasons.” But the lenient policy was updated and eliminated in 2013, leading to the most recent standoff, which Wednesday's announcement seemed to solve.

"The Air Force will be updating the instructions for both enlisted and commissioned Airmen to reflect these changes in the coming weeks, but the policy change is effective now," the Air Force said.

"Airmen who choose to omit the words 'So help me God' from enlistment and officer appointment oaths may do so."

The repeated fights over the Air Force oath highlight the fraught relationship between faith groups and military service.

Although today there does tend to be a strong correlation between military service and religious belief, particularly Christianity, this was not always the case. In fact, there was a period when Christians believed military service to be antithetical to Christianity itself.

A third-century document, attributed to St. Hippolytus and known as the Didache (“teaching”), stipulated that any prospective Christian who wanted to become a soldier should be rejected as a candidate for baptism.

One of the major problems with being a soldier in the early Christian world was, ironically, the swearing of oaths of allegiance.

By the third century, Roman soldiers were required to swear the sacramentum militare on an annual basis as a pledge of loyalty to the emperor. The Christian church father Tertullian observed that there were many Christians who happily served in the Roman military and thought nothing of swearing the oath.

But there were others, like Tertullian himself, who thought that Christians should not compromise on such an important issue. In fact, a substantial proportion of early Christian martyrs were soldiers who went to their deaths for refusing to swear military oaths.

For some Christians, then and now, the issue isn’t about what authority one swears loyalty to but about oath-taking in general. The Bible seems to suggest that Christians should simply not take oaths at all.

The Old Testament laws, the Ten Commandments, prohibit swearing falsely (bearing false witness). And according to the Gospel of Matthew, Jesus revises this commandment, saying, “I say to you, do not swear at all. … Let your word be ‘Yes, Yes’ or ‘No, No’; anything more than this comes from the evil one.” (Matthew 5:34-37).

To this day, Jehovah’s Witnesses refuse to perform military service, salute flags or swear oaths of allegiance to the state.

The current Air Force case, however, is not about someone who refuses to serve in the military because of the oath; it is about someone who wants to serve in the military, who has in fact already served his country in uniform, but who is being prohibited from continuing to do so because of the oath.

In the ancient world, it is safe to say, words mattered more: A blessing or a curse was thought to have real ramifications. Oaths, spoken in the name of the deity or the emperor, were as strong as speech could be.

Most of the power of the spoken word has drained away over the past centuries, but the oath remains and remains legally enforceable.

The historical role reversal is striking.

Christians, once forced to swear oaths to powers in which they did not believe, seem now to be forcing others to swear oaths to powers in which they do not believe.

The punishment for refusal is, of course, different: No one is being killed for failure to swear correctly, because after all, no one is forced by the state to fight in the military.

Some might think that the comparison between ancient Christians and modern atheists is a false one. Yet it is a closer parallel than it may first appear.

Atheism, as a recognized system of belief, is still in its relative infancy, as Christianity was in the Roman empire.

Federal courts have determined that, at least for the purposes of First Amendment rights, atheism is a religion, but that decision was made only in 2005.

We are, as a nation, still coming to terms with the phenomenon of atheism. The question of whether an atheist can serve in the military without compromising his or her beliefs seems like an important question to address, and to get right.

Joel S. Baden is professor of Hebrew Bible at Yale Divinity School. Candida Moss is a professor of New Testament and early Christianity at the University of Notre Dame. The views expressed in this column belong to Baden and Moss.