The Crisis of the 7th Century

I have changed the Roman Armies size to 57,500 and the Arab Army to 27,500, after averaging modern estimates from various sources.

While I now agree that 100,000 men is a rather implausible estimate, I believe the Roman Army was larger than 25,000 for a number of reasons.
First, the Army at Yarmouk was multiple armies that had been called back together. Second, even If all of the Roman Armies in the Levant were 25,000 men strong, the Arab Ghassanids contributed many men as well, increasing the total number of men by a good amount.

I still think that's a good way too high, I'm afraid. Maurice makes things very clear that 25,000 is a maximum for an early seventh century army, not an average. An average sized force would probably be somewhere between five and ten thousand men, from what I've read. So, if several armies were brought together, and add to that a few thousand Ghassanid reinforcements and you get what probably was, at the very outside, a Roman army made up of 30,000 men.
 
I still think that's a good way too high, I'm afraid. Maurice makes things very clear that 25,000 is a maximum for an early seventh century army, not an average. An average sized force would probably be somewhere between five and ten thousand men, from what I've read. So, if several armies were brought together, and add to that a few thousand Ghassanid reinforcements and you get what probably was, at the very outside, a Roman army made up of 30,000 men.

Do you recall the basis for that? As in, how that 25,000 is determined to be the maximum sized-army?

The Roman Empire of Maurice's day seems to be at a low population ebb relatively speaking (thanks to the plague in Justinian's time) and has military commitments the length and breadth of almost all its frontiers, so my suspicion is that it has more to do with a lack of manpower than a lack of an ability to support a larger force (meaning, concentrating more than 25,000 troops is more than the Roman Empire can afford to do, not a logistical concern).

Add in the devastation of the war/s after his murder/assassination, and it'd be even worse (@ Stanley).
 
Just assume it's just exaggerated historiography if you like. If they win and go on to limit the Arab conquests, then every minor power is going to say "We were there to kick those Arab bandits in the teeth too!" to inflate the numbers.
 
Do you recall the basis for that? As in, how that 25,000 is determined to be the maximum sized-army?

The Roman Empire of Maurice's day seems to be at a low population ebb relatively speaking (thanks to the plague in Justinian's time) and has military commitments the length and breadth of almost all its frontiers, so my suspicion is that it has more to do with a lack of manpower than a lack of an ability to support a larger force (meaning, concentrating more than 25,000 troops is more than the Roman Empire can afford to do, not a logistical concern).

Add in the devastation of the war/s after his murder/assassination, and it'd be even worse (@ Stanley).

I'm quoting here from page 100 of Haldon's "Warfare, State and Society in the Byzantine World: 565-1204".

On the Strategikon, Haldon states:

"An average force of between 5000 and 15000, and a large force of from 15000 to 20,000 is discussed, figures which coincide with those which can be deduced from an earlier 'official' document, the Notitia Dignitatum of the early fifth century."

Haldon goes on to suggest that the total number of Comitatenses available to the Empire at the end of Justinian's reign was probably somewhere around 150,000. Appeals from Italy under Tiberius II for more men would suggest that Italy's field armies were denuded- and he suggests also that under Phokas and Heraclius, the armies of the Magister Militum per Illyricum were destroyed altogether, a loss of around 18,000 men. Adding in casualties of the Persian wars, plus the worsening situation in Italy and the Balkans, and I'd say of all the field armies of the Empire in the 630s, we have a figure of about 100,000.

Of course, to that we should add the Limitanei, but we can assume they'd have been even more badly shredded by the Persian and Slavic invasions than the field armies were. There's evidence from Egypt that Heraclius made some effort to re-establish them, but this would have been a process that would only just be starting off in the 630s, so I'd guess no more than a maximum of maybe 25,000 Limitanei were present in the whole of the East at the time of Yarmouk.

That's why I think an army of 55,000 at Yarmouk ITTL is too large. Even under Justinian, we should note, the maximum sized army Procopius and Agathias discuss is 30,000 men.
 
That sounds like a state that would be mustering every soldier in the Levant to form this army - which neatly explains why its defeat OTL was so crushing, as well. What's left to stand in the way of the Arabs? Nothing of consequence. The Limitanei haven't reformed in full, the other frontiers still need men.
 
That sounds like a state that would be mustering every soldier in the Levant to form this army - which neatly explains why its defeat OTL was so crushing, as well. What's left to stand in the way of the Arabs? Nothing of consequence. The Limitanei haven't reformed in full, the other frontiers still need men.

Actually, the consensus is that after Yarmouk, the remaining Comitatenses (or should we being calling them Thematikoi by this point?) retreated into Anatolia in reasonably good order- perhaps 60,000 or so men, in all. The existence of surviving field armies in Anatolia explains why the Empire was able to launch an initially successful reconquest of Egypt in 645, and raid into Cilicia and Syria in the 650s and 660s. Yarmouk didn't destroy the field armies outright- it was just a bad defeat which prompted a tactical retreat that eventually became permanent.
 
Actually, the consensus is that after Yarmouk, the remaining Comitatenses (or should we being calling them Thematikoi by this point?) retreated into Anatolia in reasonably good order- perhaps 60,000 or so men, in all. The existence of surviving field armies in Anatolia explains why the Empire was able to launch an initially successful reconquest of Egypt in 645, and raid into Cilicia and Syria in the 650s and 660s. Yarmouk didn't destroy the field armies outright- it was just a bad defeat which prompted a tactical retreat that eventually became permanent.

Oh aye. What I mean is, the Empire doesn't have the forces in the area at the time to do something about it - the Levantine army (by whatever name) is destroyed, or at least crippled.

The field armies in general, not so much. But certainly a good chunk of it, and the relevant chunk, is gone.

I'd say, incidentally, Comitatenses for the immediate aftermath, Thematikoi for the ones raiding Cilicia and Syria, if I had to make some sort of standard (and hopefully I don't, as this era is as weak a point for me as post-1204 is for you, I believe).
 
With the Arab invasion army of the Levant being destroyed, I imagine the Romans will then conquer the lost territory back.

Will whoever is in charge of that army then declare himself Emperor? That was one of the problems with the Crisis of the Third Century--every victorious general tried to make himself emperor.

(Well, a bunch of them.)

Given that Heraclius should be on the throne right now and he has all the street cred from overthrowing Phocas and saving Constantinople and then inflicting truly epic defeats on the Persians, I think whoever commanded at TTL's Yarmuk would be very hesitant to challenge him.

Now, if Heraclius has a weak successor, that's something else. IIRC Heraclius married his niece or something icky like that and their kids were sickly.
 
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