What made the Roman Army so dominant?
 

Their legionnaires?

A combination of excellent equipment, excellent discipline, excellent training and excellent organisation, I'd say. Not to mention that Rome produced a large number of excellent generals in comparison to most other states.

One factor was the steel they obtained from their Etruscan and Celtic conquests.

In the beginning, they outnumbered the Etruscans and a little later they took the Celts bite by bite (after they had gotten got bit by the Celts.)

I'd just like to point out that the Romans suffered a lot of defeats in their time. The reason the Romans as a people were so dominant is that they were happy to endure them and simply grind their opponents down.

The Roman army during the Republican times was often bested or failed to win victories. In fact Roman dominance didn't as much stem from her military prowess, which was top notch don't get me wrong, but by the fact that their attitudes towards war & peace were such that they would continue to push on till and would willingly let a conflict escalate in order to win it. This attitude was unique and created some misunderstandings with hard consequences when peace finally came. When for example a Hellenistic ruler waged war he would sue for peace when things went haywire, Rome however if she lost a legion would simply send another... and another... and another... and ultimately her foe would be beaten. Moreover you cannot detach the Roman military succes from the Roman state.

It's an unpractible idea to detach the performance from the Roman army from the workings of the Roman state and Roman society as a whole.

There are a lot of good postings coming from belgium tonight.:laugh:

Moreover, once they were able to unify italy (which took very long), they had much more manpower than their enemies. Italy was densely populated. I think it had 7 millions inhabitants (less than Gaul, but Gaul was divided between many tribes, whereas all of Italy was either Roman or an ally - in fact a vassal - of Rome). This helped them during the punic wars. They also had the right men at the right moment : Scipio (who conquered Spain and North africa), Marius (saved Italy), Pompey (conquered the orient and ended the first civil war by reunifying the empire), Caesar (conquered Gaul and reunified the empire a second time) etc.

During the Second Punnic War, their manpower was 300,000 roman citizens, which with Italian allies increased to 600,000, a century after this both romans and italians accounted for more than 900,000 men available for army service.

No other state (in western Eurasia) could movilize such number of people. Being Rome behind several enemies in the military fields, man by man, it was its huge advantage on manpower what gave the edge to Rome.

And this was due to, like ancients told, the Roman Constitution. Broadly speaking, its social and political organization.

Aye, militaristic society, political system organised according in the military way, and sharing citisenship with conquered or allied nations.