Theodosius (378-395) was called the 'Great", he reunited the Eastern and Western halves of the Empire, and was the last strong Emperor of an Empire that stretched from the sands of Syria to Hadrian’s Wall in Britannia. But what if we cut the life of this great man short?
In 390 the Visigoths broke their commitments to the Roman Empire (probably due to the losses they suffered during the Maximus campaign) and invaded Thrace. In 391, Theodosius entered the province with an army to bring the Goths to heel. The rebellion brought to prominence Stilicho in 392 who became the commander of the troops of Thrace. The Gothic revolt was finally settled by negotiation and the Goths become valuable foederatti against the usurper Eugenius.
However, the Gothic rebellion was not danger-free for Theodosius. On the Maritza, he fell into an ambush and was almost killed, only to be rescued by a general named Promotus. But what if Promotus had arrived too late to save his Emperor and Theodosius died four years earlier than OTL?
Although blame is often assigned to Theodosius I (despite his military and ecumenical successes) for failing to produce a final solution to the barbarian problem, the far greater fault may lie in his continuing tendency to conduct civil wars within the Empire. Theodosius could not tolerate an independent dynasty in the Western Empire and the issue constantly had to be contested by war. The consequences of this policy were bloodshed and damage to the armies and the frontiers. In this respect, it matters less that there was a shortage of military manpower in the Late Roman Empire during the 5th century but rather that the recurrent conflicts destroyed the quality of the army in that period. The losses of highly trained Roman veterans in the ranks of the elite field armies could only be compensated for by the recruitment of either untried civilians or militarily competent but politically unreliable barbarians from across the frontiers.
The sudden death of Theodosius in 391 would immediately highlight the shortcomings of his policy towards the Western Empire. In 389 he had re-installed Valentinian II as ruler of the West after the defeat of the usurper Maximus. But Theodosius left the new Augustus as much a puppet as he had been throughout his previous reign, by installing one of his own generals (a Frank called Arbogast) as commander of the western field armies. In 391 Arbogast holds the real power in the West and when Valentinian committing suicide in 392 (which the PoD has done little to change) the Frank merely replaces him with a former teacher and civil servant called Eugenius (much as he did OTL). What would the East’s reaction be such an outrageous act of king-making?
In OTL, Theodosius refused to acknowledge Eugenius and instead invaded the West to install his own son (Honorius). In the ATL, this seems unlikely. If Theodosius had died in 391, the imperial purple would pass to his son, the weak and ineffectual Arcadius (at this moment only 15). The power vacuum left by this accession would spark off fierce competition between ambitious politicians and generals, and facilitate revolts among discontented forces within the Empire. Given the internal conflict at this ATL moment in history, it seems unlikely that the Eastern Empire would risk a war with the West.
Also the war with the Goths may still be ongoing. In order to avenge Theodosius, the war against the Goths would probably be prolonged past the OTL point of 392. Indeed, the political momentum of the time might demand the elimination of the Gothic threat or at least make a political settlement with the Goths less tenable. Given these considerations, I propose that the East Empire would prefer negotiation to war and formally recognise the usurper in the West. It is possible that war could be opened at a later date but given the challenges facing the Eastern Empire in the 390s, I doubt they will get around to it.
Would a longer reign of Eugenius mean a pagan ‘revival’ in the West? I don’t think this is likely. It was only Eugenius’ anxiety for support that led him to champion the pagan ‘party’ in the West and restore the altar of Victory to the senate house at Rome (he had previously turned down the same request twice before). In order to gain Eastern recognition and favour, Eugenius would remain at least nominally Christian, although he may repeal some of the laws Theodosius drafted in 391 (which constituted an unprecedented attack on the ancient cults). It is rather improbable that he would make the Bishop Ambrose’s cathedral a stable and conscript his priests into the soldiery.
And in the long-term? Theodosius's victory over the Western army at the River Frigidus in 394 demoralised the Western forces and weakened the defence of the northern frontier (according to Ferril as discussed in his The Fall of the Roman Empire). With a stronger Western military, it is quite possible that the barbarian invasion of Gaul (starting on the last day of the year 406) could be contained in Gaul and the Pyrenees defences could be maintained for longer than OTL which may prevent the loss of Africa. A more vigorous defence of the Rhine frontier would mitigate the civil wars of the 407-13 period and preserve a more coherent and stable Roman state into the 5th century.
Any thoughts?