"If ye be reproached for the name of Christ, happy [are ye]; for the spirit of glory and of God resteth upon you: on their part he is evil spoken of, but on your part he is glorified." 1 Peter 4:14-16 KJV
Many Christians have been and are being martyred for their faith throughout the history of the Common Era as they are being killed today because of their faith in Northern Nigeria (genocide of estimated 10,000+ during 2019) and worldwide annually (estimated to exceed 100,000 - again for 2019 - Vatican estimate 2018).
One normally thinks of Christian martyrs as having been family types or religious leaders, and not so much as having been from the military. Undoubtedly the most vivid example of the latter, Christian soldiers being martyred for their faith, was the fate of the Theban Legion of the Roman Army during 286 C.E.*
As background information on this Roman Legion, 6,600 soldiers and officers had been formed (recruited) in Upper Egypt at Thebes, and as was the policy of Rome, legions formed in remote areas were sent to other parts of the Empire.
Such was the case with the Theban Legion when it was ordered to march north to Gaul in support of Emperor Maximian campaign against Burgundy rebels. Shortly after they arrived, Maxinian ordered a general sacrifice ceremony in which all of the Legions were to participate.
When the Theban Legion learned that they would have to sacrifice to the Roman gods, they refused on the grounds that they were all Christian Coptics. The Emperor was so enraged to find that he had Christians within his armies, especially an entire legion, that he immediately ordered the death of every 10th man of the Theban Legion.
When this had been done, Maxinian again ordered the Theban Legion to offer sacrifice and they again refused, which resulted in another 660 of the legion being executed. Upon the third refusal of the Theban Legion soldiers to offer sacrifice, Maxiniam ordered the entire Theban Legion to be hacked to death with swords. (September 22, 286).**
Of all of the stories for all of the Martyrs, this one of an entire Roman Legion being martyred has reason to hit home with me.
I own a small bronze ring that was a part of the Roman Legion relics found at a battle site between the Roman Legion XII (Fulminata) and the Quadi people (Germanic tribes) in Slovakia (180 C.E.)***
It is the ring of a Christian and also that of a soldier. The face of the ring bears the "X" of Sol, and the two small crosses carved onto the shoulders of the face eliminates mistaking that ring as being for any other purpose.
How life must have been for the wearer of this ring, not knowing whether their death would come in battle or by martyrdom if their Christian faith were found out. Perhaps it was the same for the Christian soldiers of the Theban Legion. One can only help but admire the resolve all Christian soldiers throughout the second and third centuries C.E. who stood steadfast in their faith unto death.
Note: The area around Thebes was filled with Coptic Christian Extremists who were the best fighters in the area. When they were recruited into service, it would have been for their ability with weapons, without much further interest or inquiry into anything else. That was a serious mistake that would not have went unanswered in following up on the case and fate of the Theban Legion.
* The Maximian period is known as the Sixth Primitive Persecution in Fox's Book of Martyrs.
** R. Van Dam, Gregory of Tours: Glory of the Martyrs (Liverpool, 1988), 85.
*** Marcomannic Wars, 176–180 AD.