A North Africa that Rome never took back. The Vandals were a tricky bunch, and even at their lowest point, they were able to out-smart and beat back a Roman force that greatly outmatched their own forces.
That doesn't mean they
can't take it back. Majorian could have very well discovered the treachery ahead of time. As for the 467 invasion I attribute the defeat largely to Basiliscus' incompetence and some meddling by Ricimer (who may have not wanted the invasion to succeed for personal power reasons-him and Leo didn't see eye to eye on who should be emperor in the west to put it nicely, and Anthemius would be given a lot of legitimacy and political capital if the invasion succeeded. That would likely translate to the end of Ricimer and he knew it.
But could a Majorian or Ricimer really do that well with the Huns pressing in on them? They were opportunists who really found themselves largely employing many that used to work for Attila, like Odoacer and Orestes.
Could a Majorian? Well the key here is what happens in the 450s. The loss of Gaul occurred after Aetius' death and the power vacuum that erupted from it. If Aetius is surviving here-and he very well may, the butterflies with this POD could be enormous, there doesn't
need to be a Majorian to have one last go at restoration. The western empire was not teetering on collapse under Aetius, but it was tenuous. His assassination was literally the worst thing that could have happened because of the power struggle that followed. If Aetius survives, that changes everything. He likely has important contacts in North Africa from his power struggle days with Boniface, and it's not like the Vandals were unwilling to play politics with the Romans.
Anyway, I think one important thing is being understimated here: By and large, invading the WRE was not really worth the effort for Attila. The west was at the very edge of his logistical capabilities and political control. That was probably the biggest factor in his withdrawal after his first invasion, and probably behind why he didn't press forward after sacking Aquilea. Add on the fact that there wasn't much tribute to exact out of the western empire, and it simply did not have a good enough benefit for the cost to waste time on after the first two failed attempts. The east was far more lucrative, and Attila could more than sustain his power on the tribute from the east alone.
Okay. So Attila died in 453. The Romans attacked North Africa in 467. That's 14 years, not 6. Majorian attempted to gather a force of mercenaries in Spain to take the fight to the Vandals, but they beat him before he could. Again, the Vandals were quite wily. I don't think we should downplay that pretty crucial fact.
I was referring to Majorian's attempt. They were, but it simply takes one traitor (since it appears the Vandals may have bribed Roman crews/captains to assist in burning the ships) to warn Majorian for the plan to fall to pieces. Not to mention, as I said, Aetius almost certainly has important political contacts in North Africa that Majorian simply did not have. They would be invaluable in figuring out the Vandals strategy. Regardless, the Vandal's maintaining control of North Africa was not a fait accompli especially if the west is more stable in this scenario with Aetius living.
And it appears that Attila wanted much more than tribute. He invaded Gaul with the intent of conquest, not tribute. He demanded half of the WRE as a dowry to his engagement to Honoria, which he had every intent of legitimizing. Italy, yes, he would have gladly just exacted tribute from them. Things seem murkier in the Balkans, but in the end the ERE was usually able to pay him off after he burned the countryside to nothing.
It was a pretext nothing more. Attila did not, nor could he sustain, a conquest. It simply would make no sense. His logistics were stretched to the maximum in his invasion of the west already. Attila's not insane and suicidal. All he wants, and all he requires, is tribute. I would reference Peter Heather but I don't have the book on me right now. Regardless, if Attila went for conquest, it would be the biggest mistake of his career.
And "beaten back twice in the West" is a bit misleading. Defeated once in battle is really more accurate, and considering the Roman track record previous (and after) the Battle of Chalons, that doesn't seem to matter much. He invaded Italy, sacked several Northern Italian cities and didn't turn around because Aetius was so awesome, but because there was a famine in Italy at the time and plague had broken out in his ranks. Under more suitable circumstances, Attila could have burned the whole peninsula to the ground, and Aetius couldn't have done squat to stop him.
His logistics were also stretched to a breaking point. He
could not sustain an army in the west for very long. He didn't retreat after Chalons because it was a defeat. It really wasn't. He retreated because, again, he could not sustain an army that far west for any length of time. I believe with the second invasion the east counter-raided Hunnic territory anyway, which also contributed to Attila's withdrawal. Attila cannot simply take an army wherever he wants.
A nuisance? I'm sorry amigo, but you have the worst habit of downplaying people other than the Romans. Let's recap on Attila's track record on wiping the floor with the ERE, shall we?
440: destroy Viminacium in what's now Serbia. Also captured the city of Margus in the same region.
441-2: sacked Margus, Viminacium, Singidunim and Sirmium.
443-5: took Roman military centers of Naissus and Ratiara, as well as taking Serdica, Philippopolis, Arcadiopolis, and destroyed the Roman army outside Constantinople. Defeated another Roman army at Gallipolis. Only turned back because they were unable to breach the double-walls of Constantinople (which were built to keep the Huns out, by the way). Completely stripped the ERE of any military options in Europe.
447- Defeated ERE army at Utus. Raided unopposed as far as Greece. A contemporary account from the time in Constantinople:
Which again, never directly threatened the existence of the ERE. Constantinople could never be taken by Attila, and he knew it. Even after the earthquake, a siege of Constantinople would have been very lengthy and Attila would have been boxed in in the process and destroyed. If anything, that was exactly what the eastern commanders wanted. By nuisance I mean Attila posed no existential threat to the eastern empire.
"The barbarian nation of the Huns, which was in Thrace, became so great that more than a hundred cities were captured and Constantinople almost came into danger and most men fled from it. ... And there were so many murders and blood-lettings that the dead could not be numbered. Ay, for they took captive the churches and monasteries and slew the monks and maidens in great numbers."
—Callinicus, in his Life of Saint Hypatius
I think you underestimate the ability for exaggeration. I also am not going to take very literally a source written by someone in the 7th century about a 5th century occurrence. Were the Huns terrifying to the people of the Balkans? Yup. Did they prove a serious problem for maintaining stability and economic well being in the Balkans? Yup. Were they ever an existential threat to Constantinople? Nope.
Hardly sounds like a nuisance, considering the ERE was never able to mount a successful defense against him, and he twice threatened the capital.
He never actually had any shot at taking the capital. This is what would happen if he went for Constantinople (and Attila was directly aware of this, which is why he never tried it). He would be bogged down in a lengthy siege he could never win. Roman field armies in the Balkans (who normally never engaged in a field battle with Attila and so would be very much intact), would surround him. Attila would be trapped and doomed. And again,
why would he want to destroy the eastern roman empire? It was far more politically and militarily expedient for him to raid the Balkans, sack a few cities, and demand an increase in tribute (or demand the resumption of tribute), which the ERE almost always obliged. His raiding rested on him maintaining political power at home and that was largely achieved through military might and/or bribing his court lavishly. Which is why all his raids in the east ended with a demand for tribute and never were aimed at destroying the ERE.
Indeed, Attila did not want to see the Empire destroyed, but he also did not want to see it revive. During this time, he had the upper hand, and it was one of the few times in history where it was the Romans who were being played by the barbarians. And even still, I don't think he could hold back the Visigoths who had already taken vast swathes of the WRE from taking even more, or the Allemanni, who invaded Italy in 457. The WRE is doomed to fall apart, or be integrated into the East, which itself is in a compromised position.
Again, all of that was a direct result of the assassination of Aetius. With Attila surviving you vastly increase the chances of Aetius surviving. Aetius was instrumental in holding the WRE together and it's clear he was making moves towards getting one of his own on the throne to shore up his legitimacy. With a couple years of butterflies in between, Aetius' chances of living are substantially increased.
Recall that the Vandals sacked Rome 455. Hardly sounds like the Vandals were the ones in decline at that point.
Because, again, the Roman state practically collapsed following Aetius' death. I'm not saying the Vandals were not a force to be reckoned with, far from it. What I am saying though, is Genseric is to the Vandals what Aetius is to the Romans-the guy holding everything together by sheer force of personality and ability.