I can hear the Ben Stein-esque voice of my high school history teacher saying…“Empires fail when they exceed the reasonable reach of their supply chain.”
Britain was a problem for the Romans because it was too far away and the difficulty of bringing in supplies and reinforcements was magnified by the necessary ocean crossing. Even more so for Ireland. While they probably could have persevered and conquered the entire area, there was little there for them to gain once they’d overtaken the southern portion of England. The costs of maintaining their rule over these far-flung lands was high and the return on investment was low. The natives weren’t rich civilizations with storehouses of assets to be sent back to Rome in tribute.
I guess what I was trying to say earlier is that I think that there may be a bit a Texas sharpshooting going on when talking about Roman expansion.
If Caesar hadn’t conquered Gaul in seven years, people probably wouldn’t have thought the Romans capable of conquering Gaul in seven years. Look at Spain. The Romans began conquering the Iberian peninsula during the Punic Wars. The Cantabrian Wars took place during the time of Augustus. That’s two hundred years, folks.
Similarly, we’re all going around explaining why the Romans didn’t conquer Germania to the Elbe, as Augustus wanted, but instead ended up stopping at the Rhine. And yes, there are obviously reasons for that. But if they *had *conquered Germania to the Elbe, that may not have been surprising to anyone. The fact that they didn’t doesn’t meant make it inevitable that they didn’t.
“Let’s go out conquering the entire world” was never the Roman project. There was never* a *Roman project, singular. Every territory added to the empire had its own context and was taken for different reason, in different circumstances. Taking over Greece was a massively convoluted affair involving any amount of political back-and-forth before the area was finally incorporated in the empire as a number of provinces. At times in their history, the Romans were surprisingly reluctant imperialists. Sure, at times they overran large areas in no time flat, but at other times they hemmed and hawed over places the size of a postage stamp. Sometimes areas were taken and then abandoned. Sometimes you get an expansionist Trajan followed by a “pacifist” (quotes because it’s actually more complicated than that) Hadrian.
If someone, for some reason, had said, “right, all the resources of the Empire will now be put to use for conquering Scotland and Ireland”, (in order to, I dunno, win a bar bet, I guess, this is a hypothetical) then things may have been different. But no one ever said that, because no one ever had a reason to. Agricola’s campaigns and the adventures of Septimus Severus were on a more limited scope.
TL;DR: That they didn’t isn’t in itself proof that they couldn’t.
BTW: I should add the corollary, because now I made it sound like the Romans could have conquered from here to China if they wanted to. Obviously not the case. So, the corollary: When the Romans did overrun large areas in no time flat, that would usually be because of some pretty darned specific circumstances. Again, Gaul. That’s bordering on “fluke”.
Yeah, I know, keep politics out of this. But there is something hilarious about seing Crassus, Mark Antony, the emperor Julian, etc, going off on military adventures in the Middle East and making a mess of it. The more things change, and so on.
Caesar died with plans for invading Parthia sitting on his desk. That gives me comfort. Maybe being stabbed to the death on the senate floor wasn’t the worst possible outcome, if going to Mesopotamia and ending up looking like a dick was plan A.
If you look closely, you’ll see the Romans pretty much built their entire western expansion on conquering the Celts. They were good at kicking Celtic ass.
Ireland? Just a land too far with not enough economic value.
But the Gauls had invaded Rome–they were considered a threat, whether or not they actually were when Caesar went looking for wealth & publicity. Invading Britain was stretching it & Ireland was probably just too much trouble.
(I remember an episode of Hercules in which Caesar (Karl Urban) attempts to conquer Ireland. Hercules foils the attempt. So Caesar leaves–dumping his scribe into the Irish Sea on his departure. He only wanted to record his victories!)
Even Trajan didn’t bother to escalate things in Britain. Which should probably tell us something.
Invading Britain at all, in the first place, isn’t an entirely obvious thing to do. Caesar, being Caesar, had a stab, but then went “nah, screw it.” Augustus didn’t do it. If Claudius hadn’t needed some military glory on his resume, then who knows, maybe no one ever would have.
I’m not entirely sure what Claudius’s long-term idea was, anyway. I’m pretty sure it wasn’t “in a century or two, someone should build a wall half way up the island.” But I also can’t really see it being “we’ll conquer this joint all the way up until we run out rainy craphole.”
“Someone can cross that bridge when they get to it” seems more likely.