Centurion Position in Battle

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- I am utterly comfortable seeing the optio as a platoon/century sergeant, because I see it as an obvious parallel. But either way he is also synonymous with the Greek file-closer, although there is only one of him. I see him outside and to the rear of the 60-man formation, because he has to keep all the files closed up - is that a wrong assumption?

I really think we should try to get away from modern comparisons like this. The optio was the second in command of the century, or even shared command of the century as necessary. If you call him a platoon sgt it means different things to different people.