Archaeologists Find Athenian Naval Base

[Banjo]

So many citizens had perished in earlier wars. The second Punic war devastated the "Roman" citizenry. 30,000 at Trasimene, 60,000 at Cannae. By the time Iulius was in Gaul many soldiers were regular folk.

Everything I read underneath is correct too. The Gracci etc.

Rome simply ran out of Romans and then as the empire grew Africans, Greeks, anyone could be in the legion. Later they hired mercenaries. Especially in the east. 

That of course was centuries later.

One of the promises Caesar made to form his leadership was to offer his men land, and the citizens jobs whereas they had been "taken" by slaves. Caesar was the "Man of the people" and many fell for it.

Mind you, who else would work the lead mines but slaves?

Later those same soldiers felt cheated, civil wars and strife. Down went the Republic. All hail Octavian.

2nd Punic war didn't deplete Rome's eligible manpower.  Rome continued to be able to field fully manned militia army for wars on multiple fronts through the 3rd Punic war.   Later social and economic factors alluded to earlier depleted the ranks of yoeman farmers, and also made those who remained unwilling to serve.  The transition happened way before Caesar, under Marius at around 110BC.  

The Roman army had always consisted of "everyday folk".  Prior to Marius, the army consisted of Yoeman farmer citizens who had some small property, and the ability to purchase and hand down through the family a set of soldier's equipments.  After Marius the army increasing consisted of the dispossessed citizens who can't pay for their own equipment and relied on the state, and their generals, for basic equipment kit.

Even during caesar's wars, not everyone could be in the legionary army.  One has to be a Roman citizen.  That usually means one had to have been either a true Roman, or from an Italian city long allied with Rome and whose citizens were granted Roman citizenship at the end of the social wars.  The phenomenon of a permenant auxiliary army that consisted of non-citizens didn't really arise until after the start of the empire.

Later Roman legionary army didn't really become open to everyone until around AD210, when serverus granted Roman citizenship to all freemen in the empire.

Well there were other battles and Cannae and Trasimene happened over a fortnight.

The key here is Citizen. One had to be a citizen to join up. Buy their own gear. Farmer or politician.

I think the Roman , say at the time of Diocletian, was quite different to those who fought under both Pliny's. One successful, the other not.

Indeed, we have biological evidence centurions at a later date came from all over the empire. People Africanus would consider barbarians. 

I do of course also agree with you. Just adding to it, if you will.