Thread by @byzantinemporia

Rome’s wars on the eastern front were a macrocosm of how they fought battles:
Heavy Roman forces in the center, allied auxiliaries on the wings.

Thread.

The classic Roman battle formation placed the legions in the center, the heavy infantry that was the bread and butter of the Roman army.

On the flanks were the auxiliaries, specialty troops such as light infantry, archers, and especially cavalry.

Roman homegrown cavalry was comparatively far less good than its infantry, so they often outsourced it to allies. From the wings, these auxiliaries could harass the enemy’s flanks and pursue him when he broke and ran. But they were rarely what won the battle.

The Battle of Zama is a good template:

-Both armies lined up in standard formation
-Roman center holds against Hannibal’s elephants as the cavalry fights on the wings
-Infantry clashes as Roman cavalry pursues
-Cavalry comes back to mop up

At Zama, Scipio focused his attention on the center, trusting his cavalry officers to do what needed to be done on the flanks.

How did things appear to Roman emperors looking east?

On the left, the Armenian mountains separated Asia Minor from Persian Azerbaijan.

On the right, the Arabian desert separated Syria and Palestine from lower Mesopotamia.

Only in the center, in upper Mesopotamia, was it possible to bring large armies together.

The Tigris, Euphrates, and their tributaries were not only useful corridors for bringing men and supplies to the front, but were fertile enough to provision massive armies—up to 60,000 men fought at the Battle of Carrhae alone.

This was also the easiest sector to reinforce. Reserves could be marched in from Anatolia or landed on the Syrian coast.

Not so much on the flanks. Armenia was more of a protectorate than an actual part of the empire during Roman domination.

Such a mountainous country was always hard to control, ruled more by confederated princes than a central authority.

Both Romans and Persians adapted to this reality, working more through local princes rather than try to administer the country directly. Both sides still marched armies through Armenia, but it was much more a fight between auxiliaries.

If the mountains of Armenia were tough to control, the deserts of Arabia were even harder. There it was a long-running skirmish between tribal confederations: Roman-allied Ghassanids against Persian-allied Lakhmids.

These flanks were important but rarely decisive. Only in rare cases, like the 602-28 war when the entire Mesopotamian front collapsed, did a Roman army do what Heraclius did and attack the Persian capital by outflanking the center.

This mirrored Alexander at Gaugamela, where Alexander deliberately let his center collapse in order to sneak around with his cavalry and attack Darius’ headquarters in the rear.

More typically, the two sides just slugged it out on the northern Mesopotamian plains, where a series of fortress and parallel rivers meant that even the winner of a battle could only make marginal gains.

Sort of like World War I, in a way.