Why was a'classic' centurion in charge of only 80 men?

[Silent bob]

Has anyone ever wondered where a Centurions other twenty men where?

In the most quotes organisation 10 units of 8 'tent buddies' equals a Century commanded by a Centurion......sorry....that's 80 men?

Was it just a quaint old throwback to an earlier age or did his 'charges' include servants and Non Coms?

Did he nominally have 20 men back at the legionary base as replacements/recruits?

Ta

SB

[dadlamassu]

Under the Principate (the period I know most about) the grade "Centurio" covered many of what we would now call ranks.  I have read reasonably widely on the Roman Army and sources vary.   The grade holder originally probably did lead about a hundred soldiers.  That said the basic unit of the army was, on papyrus/parchment, the Contubernium of 8 soldiers who may or may not have had 1 or 2 slaves or servants and sources vary on whether these had any combat role.  Ten of of these made up a Century so, at full strength, the Century may have had 80 soldiers and 20 servants.

Now also bear in mind that the senior Centurion of the Cohort commanded the whole unit of 6 Centuries (480 soldiers and their servants and slaves) as well as his own Century.  Any of the Centurions may well have had additional specialisms as well - artillery for example manning the scorpions, onagers, ballisate etc. 

Then the senior Centurion (Primus Pilus or "First File") of the 1st Cohort (double size) was a very senior position and was part of the Legate's command group. 

So in reality a Centurion may command between 80 soldiers on promotion to Cohort command of 480 soldiers and eventually to the larger 1st Cohort of 720 to 960 soldiers (again sources and periods vary) if he rose to Primus Pilus. They were mostly of Plebeian status and rose from the ranks. 

The Centurion grade covered many command appointments.

There are many more here who are more qualified than I am to answer this fully.

[Cubs]

My understanding was that a centurion used to command 100 soldiers, but over time the Roman army was reorganised and the number under their command changed, although the title stayed the same.

[olicana]

That's my understanding too. Instead of "century" think "Century", then simply translate that to "Company" or "Battalion".

A similar thing happened to the British in mid 1800s. When the British adopted the rifle and light infantry tactics for all they lost the Grenadier and Light companies; they were not replaced. The battalion thus dropped from ten companies to eight, and manpower dropped accordingly with it. The "Battalion" remained a "Battalion" even though it was 20% smaller.

[Sir Barnaby Hammond-Rye]

Maybe it is a reference to ability? The finest among any hundred others.

Only those that meet that standard are promoted to the rank.

[Rochejaquelein]

I pulled out my osprey book on monarchist and republican centurions. Apparently the source of the word centurion/centurio is a bit debated. A now lost tactical manual by Paternus states that the original pre-hoplite warbands of Romulus were grouped into bands of 100 with a leader assigned to each (proto-centurion). The name stuck through the centuries due to having the same role on the battlefield I'm guessing.

[Cat]

Yes, a century in military terms translates better as a company.
 
Also of note from the Lewis & Short Latin Dictionary, a centuria is one of the 193 orders into which Serivus Tullius divided the Roman people and the voting assemblies of those groups.

[dadlamassu]

Even today military ranks can hark back to previous times for example:
Lieutenant = literally in French "place (lieu) holder (tenant)"who took the place of a commander in his absence
Colonel- from obsolete French coronel (earlier form of colonel ), from Italian colonnello ‘column of soldiers’, from colonna ‘column’, from Latin columna . The form coronel, source of the modern pronunciation, was usual until the mid 17th century
RAF "Squadron Leaders" now rarely command squadrons

Going back to Ancient Rome the Decurio (Leader of 10) in the cavalry commanded a Turma of 32 troopers.

Just as we do now, the Romans did then - using traditional ranks that are long past their original use.

[cadbren]

You can add the hastati to the explanations given above. Named for the hasta (spear) they carried, they formed the front ranks of Republican Roman armies from the time the Gauls sacked Rome around 390BC until the Marian reforms in 107 BC. They only carried spears for about a century if that, for the remainder of the period they carried the gladius but the name still stuck. Similarly the second rank, the Principes were so named because they were originally recruited from wealthier families, in later times they were made up of the more experienced soldiers but again the old name stuck.

[olicana]

Even today military ranks can hark back to previous times for example:

My personal favourite is Feldwebel (now German sergeant ?). Dates back to the Landsknechts. Literally, it means "field weaver", a title given because the Feldwebel was in charge of a file of pikemen, it was his responsibility to 'weave his strand' into the pike square. German poetry, lovely.