Arrian of Nicomedia (c. 86/89 – c. after 146/160 AD) or Lucius Flavius Arrianus was a Greek historian, public servant, military commander and philosopher of the Roman period. Flavius Arrianus wrote one of the most interesting and important sources for the battle tactics of the imperial Roman army.
In 134, the Alans, a tribe from the steppes of Kazakhstan, threatened the Parthian and Roman empires. Arrian of Nicomedia was the governor of Cappadocia, he took his two legions XV Apollinaris (stationed at Satala) and XII Fulminata (stationed in Melitene) into the field and defeated the invaders before they could become dangerous. He was later to publish an Ektaxis kata Alanon (Order of battle against the Alans), in which he offered advice to other Roman commanders on fighting against nomads (which is one of the few surviving sources on the marching order and battle formation of the Roman army).
Ektaxis kata Alanon
At the van of the entire army should be mounted scouts deployed in two contingents with their own commander. Behind them the Petrean horse archers, these also in two divisions: the decurions should lead them. At their rear should be deployed those from the wing of the Auriani. Those from the Fourth regiment of Rhaetians should be stationed with them, led by Daphne the Corinthian. Behind them those from the wing named Colonists. Stationed alongside them should be the Ituraeans and Cyrenaecans and those from the First Rhaetian. Demetrius should command all of these combined. Behind them the German cavalrymen, these too in two divisions, and a centurion should command them, the one in charge of the camp.
Behind these the infantrymen should be deployed, their standards carried before them, the Italians and those present of the Cyrenaecans. Pulcher, who is in charge of the Italians, should command them all. Behind them should be the Bosporan foot soldiers, commanded by their leader Lamprocles, and at their rear the Numidians under their commander Verus. The formation should be four soldiers wide. The attached archers should be at the front of their own units. The cavalrymen organic to the units should guard both flanks of the formation. Behind them should come the guard cavalrymen, and behind them the legionary horsemen, then the catapults, then the standard of the Fifteenth Legion, and with it the commander of the Fifteenth Legion, Valens, and the subordinate commander, and the tribunes and the centurions of the first cohort. In front of the standard the infantry javelineers should be deployed. These foot soldiers should be drawn up in fours. Behind the Fifteenth Legion the standard of the Twelfth should be deployed and the tribunes and centurions around it. This legion should also be drawn up in fours.
Behind the heavy troops the allied force should be formed up, the heavy armed from Little Armenia, and Trabzon and the Colchian and Rhizian javelinmen. Behind them the Apulian infantrymen should be deployed. Secundinus, who is in command of the Apulians, should lead the allied force as a whole. Behind them should be the baggage train. The wing of the Dacians and their wing commander should act as rearguard.
Centurions who are selected for this particular task should keep the flanks of the infantry in order. The Galatian wing should ride along both flanks in a single file as a guard, and the horsemen from the Italians as well. Their wing commander should ride along the flanks.
The overall army commander, Xenophoon, should lead most of the time in front of the infantry standards, should ride along the entire marching formation, and he should see to it that they march in formation, and place those in disorder back into the formation, and he should commend those that are in proper order.
This should be the marching order. On arrival at the planned spot, the entire cavalry should circle around to form a square, scouts must be sent to overwatch positions to look for the enemies. Next they should arm themselves, and after kitting out take up position in the battle formation. The battle array should be the following. Each wing of the infantry should hold high ground, as the full deployment must be in this order. On the right flank should be deployed the Armenians with Vasakes and Arbelos, holding the highest part of the flank, because they are archers all. Positioned in front of them must be the infantrymen of the Italian regiment. In command of all these should be Pulcher, who is in charge of the Italian regiment. Both Vasakes and Arbelos with their cavalry and infantry should be arranged in support of him.
On the left flank the Allies from Lesser Armenia an the light armed from Trapezus and the Rhizian javelinmen should be arrayed holding the highest part of the flank. Deployed to their front must be the two hundred Apulians and a hundred of the Cyrenaicans, in order that the heavy armed are a bulwark for the javelineers, they can hurl their javelins overhead from the high ground. The Fifteenth Legion’s infantry should hold the entire right center above the middle of the whole area, because they are by far the most numerous: the infantrymen of the Twelfth Legion should hold the remaining space on the left filling it up to the point of the left flank. They should deploy in eight ranks and their deployment should be close ordered. And the front four ranks of the formation must be of spearmen, whose spearpoints end in thin iron shanks. And the foremost of them should hold them at the ready, in order that when the enemies near them, they can thrust the ironpoints of the spears at the breast of the horses in particular. Those standing in second, third an fourth rank of the formation must hold their spears ready for thrusting if possible, wounding the horses and killing the horsemen and put the rider out of action with the spear stuck in their heavy body armour and the iron point bent because of the softness. The following ranks should be of the javelineers. The ninth rank behind them should be the foot archers, those of the Numidians, Cyrenaicans, Bosporans and Ityraeans. Artillery pieces must be deployed on each flank to fire at the advancing enemies at maximum range, and behind the whole battle formation.
The entire cavalry arrayed together in eight wings and squadrons must stand next to the infantrymen on both flanks, having the heavy armed and archers as a screen, two companies and in the middle of the formation six companies [ Gap in text ] the horse archers among them must form close to the battle line in order to shoot over it. The javelineers, spearmen, swordsmen and axe-men must guard both flanks and await the signal. The picked cavalrymen should bewith Xenophoon himself, and two hundred infantrymen from the legion, the bodyguards, and the centurions attached to the picked cavalrymen and the commanders of the bodyguards and the decurions of the elite soldiers. There should be with him [ gap in text ] a hundred light javelineers in order that while riding down the entire formation he can note and amend things if something is lacking. In charge of the entire right flank along with the cavalry must be Valens, who is commander of the Fifteenth Legion. The tribunes of the Twelfth should do so on the left.
Once thus arrayed there should be silence until the enemies come within missile range; when in range the loudest and most intimidating war cry must be raised by the whole lot, and bolts and stones must be fired from the artillery pieces and arrows from the bows, and javelins by both light armed and shield bearing javelinmen. Stones must also be thrown at the enemies by the allied force on the overwatch position, and the whole missile rain must be coming from all sides to make it concentrated enough to panick the horses and destroy the enemies. And the expectation is that the Scythians will not get close to the infantry battle formation because of the tremendous weight of missiles. If they do close in though, the first three ranks should lock their shields and press their shoulders and receive the charge as strongly as possible in the most closely ordered formation bound together in the strongest manner. The fourth rank will throw their javelins overhead and the first rank will stab at them and their horses with their spears without pause. After repulsing the enemy if there’s a clear rout, the infantry units must clear lanes and the horsemen should advance, not all squadrons, but only half of them. Those to the fore must be the first to advance. The other half should follow those that advance, in perfect formation and not in hot pursuit in order that they may continue the initial pursuit with fresh horses in case there is a complete rout, and in case they turn about to attack, they may assist those in pursuit. At the same time the Armenian archers must advance shooting their bows in order to prevent those in flight from turning about, and the light armed javelineers should advance at the run. The infantry formation should not hold its ground, but should advance at faster than the normal step in order to be a base of defence for the cavalrymen if there is stronger resistance by the enemies.
These things should happen if the are put to flight after the first charge. If they about-face and circle around the flanks, the flanking bodies of lightly armed archers should extend formation to the high ground. I do not think that seeing that the flanks become weaker through extension in this manner they will break through them and cut up the infantry. Should they overcome one or either of the flanks the horses would necessarily expose their flanks, their spears at a right angle. In that case the cavalrymen must attack not with a missile shower but with swords and and axes. The Scythians being lightly armed and having unprotected horses [text breaks off ]