In the Roman Army was a Cohort the equivelant to a modern army company. I know that a Tent was the smallest Roman unit, a bit like a modern day infantry section.
And was a Tribune similar to a Colonel.
Scott

OK....I did a google on Roman Army (you should take the time to read the article on the Roman Army organization). But

a legion was around 6,600 fighting men....so lets say a division. It was made up of 10 cohorts roughly a battalion and there were 6 centuries in a cohort...so these would be companies. The Legatus commanded the Legion and had 6 tribunes working for him, so I guess their equivalency would be a full or Lt Col. Of course this organization is post Julius Ceaser, they had other arganizational arrangements earlier

Hi Scott

The basic unit was the tent group ( contubernium ) of 8 men, 10 of these plus a few NCOs - Centurion, optio, tesserarius made up a century. There doesn't seen to have been a platoon-sized level. Originally, centuries were paired to form maniples (literally 'handfulls') but this was a Republican thing usually - interestingly it survived in the layout of fortresses where the barrack block for centuries were ordered in facing pairs. Six centuries formed a cohort (though in the 1st century AD the 1st Cohort was double strength) and ten cohorts plus a small cavalry contingent made up a legion.

Of course this makes a century less than 100 men, but the barracks in Caerleon fortress have rooms for 12 contubernia ........

Note that this is the classic organisation, the Roman army lasted nearly a millennium and underwent many chages over that time.

Tribunes were usually younger men, doing military service as part of their political career before moving on to the senate, and didn't really function like moden officers, they would have relied heavily on the long-service professional centurions for any military decisions.

David