It could be argued that the loss of Africa to the Vandals under Geiseric did more harm to the Romans and their Empire than any other event in the 5th century. Some historians have gone even further saying that if it had not been for the Vandals, the Western Empire would have weathered the storm. So let us get rid of the Vandals and their invasion of Africa. A possible point-of-divergence is provided to us by the 5th century historian Renatus Frigeridus, who gives us the following account concerning the Rhine crossing of 406/7: "The Vandals were struggling in their war against the Franks, their King Godigisel was killed, and about twenty thousand of their troops had been slaughtered so that the entire nation of the Vandals would have been exterminated, save that the forces of the Alans came to their rescue in time". So-what-if the Alans had not arrived in time to prevent the wholesale slaughter of the Vandals?
But, of course, there are other possibilities for this “no Vandal invasion of Africa scenario”. The comes per Hispania Asterius could not intervene in the 419 war between the Suevi and the Vandals: the Vandals may conquer the Suevi and establish a permanent kingdom in northern Spain (and not move southward into Baetica) or might be seriously exhausted through warfare (in which case their subsequent invasion of Baetica could be defeated). Another option could be that the comes domesticus Castinus successfully crushes the Vandals in his 422 campaign (the POD could be that he is not betrayed by his Visigothic troops). Any other ideas?
So the barbarians end their migrations in Spain, and Baetica remains in Roman hands acting as bulwark against southward barbarian raids. There is no one for Boniface to (supposedly) invite into Africa to aid him and he is probably defeated by the Goth Sigisvult in 428, thus sparing the Western Empire a particularly destabilizing civil war in 432.
The consequences? By far the most important consequences are economic and strategic: The loss of Africa not only removed the wealthiest provinces (described by Peter Heather as the economic “jugular vein of the Western Empire”) from Roman control but also exposed the Mediterranean (especially Italy and Greece) to pirate raids. Retaining Africa will, if not avoid than at least, mitigate the severe OTL financial crisis of the 440s. The Vandal invasion also robbed the Empire of one of her last unique advantages: sea-power and with it control of the Mediterranean. A “no Vandal invasion of Africa scenario” would give the Western Empire a naval edge that it did not possess post-435 and allow it to better coordinate military and economic operations against the barbarians.
Therefore Aeitus is in an even more secure position than before and his strategies could be more effective. Throughout the 430s and early 440s, the “man behind the throne” of the Western Empire, used increasing numbers of Hunnic mercenaries to maintain the northern frontiers, suppressing the Bagaudae and enforcing the loyalty of the ‘federate’ territories. The main criticism of this approach was that he concentrated on Gaul to the neglect of the other provinces (especially Africa). If there is no barbarian invasion of Africa, and Baetica acts as secure defensive safeguard against such an invasion, than this is a more successful strategy than OTL. Maybe we will see weaker Visigoths? Any thoughts?
Will a “no Vandal invasion of Africa scenario” allow the Western Roman Empire to survive into the 6th century and beyond? Maybe but the PoD has not altered the fact that the Empire is still suffering from significant manpower, territorial and economic deterioration. The Hunnic invasions and wars of this century (which the PoD has done little to change) will still leave large swathes of Gaul and Italia devastated and although the Western Empire will survive these invasions, the cost in money and manpower will still be enormous. Moreover the fall of the Hunnic Empire will also prove disastrous: the disappearance of Hunnic power will prompt the Hun’s Germanic vassals to seek greener pastures inside the Empire. Far worse, though, will be the effect on the ‘federate’ barbarians within the Empire. Previously Hunnic power had been used to contain the barbarian ‘federates’ and minimize their political influence. Now these kingdoms (not failing to note the weakness of the Empire in the aftermath of the Hunnic wars) will pursue expansionist policies. All this suggests to me that there is no hope for an imperial restoration that will place the Western Empire back in the position that it enjoyed in the 4th century. Britannia will remain abandoned, and there is little hope of the Empire holding Gaul (outside of the Mediterranean lowlands and maybe the Rhône-Saône Valley) and Spain (outside of Baetica and maybe isolated pockets on the Mediterranean coast).
But the Roman Empire could survive as a Mediterranean-based power centred on Africa and Italia. This much reduced and weaker Empire would still control Western Mediterranean commerce and the important grain surpluses of Africa, advantages that would give it a strong strategic niche in ATL Medieval Western Europe. But what would such an Empire look like? How would its ATL Emperors deal with the problems of the Late Roman Empire: a Germanized army, a powerful and hostile senatorial aristocracy and new (and aggressive) barbarian neighbours?
Any thoughts?