Late Roman Unit Sizes

[ValentinianVictrix]

'You have my vote on the splitting into Iuniores and Seniores. But why name them Seniores? It originally described those over the military age who were levied to garrison Rome. '

I was actually reading about this very topic this week. It appears that one idea is that the Seniores contained the troops with the most experience, whilst the Iuniores were originally made up of newly recruited men. So when the legion was divided into two halves, the half containing the Seniores would have had the veterans, the Iuniores would have contained those with less experience.