Quote Originally Posted by TinCow
The first cohort in a legion was usually slightly larger than other cohorts and it was composed of veterans. It was pretty much the elite cohort within the division. Some historians think there might have been an ascending hierarchy from 10th to 1st cohorts in terms of abilities and promotions, but most historians see 2-10 as identical units and only the first cohort as special.
in a battle line they had the best men in the 1st and 11th cohort, on each side of the line then moveing inward, haveing the newest troops in the center.
in other words 1st+11th = elite
2nd+10th= vets
3rd,4th, 9th, 8th= regulars
5th,6th, 7th = regular to green

they put the best on the flanks for obvious reason ...