Anyway, I've been meaning to talk about Asur military organization for some time, and finally got the inspiration to finish writing it up. Now, canon does mention the names of the units they use- companies, regiments and legions -but not how large those units are supposed to be, how they relate to each other and how they are led, which is why I'm writing this, to fill in those gaps.
The Asur military can be split into two rough groups: the professional forces, consisting of noble retinues, various warrior-orders and the like, and the militia. The militia can then be further subdivided into the active-duty militia, formally known as the Royal Army of Ulthuan, consisting of citizens serving their tour of duty under the Phoenix King's banner, and the reserve militia, which consists of those who have finished their tour but can be called up by their nobles as needed. In active-duty units elves from different kingdoms and colonies are mixed together down to the squad level, while reserve units are formed from local communities, fighting alongside their family and neighbours. While the Silver Helms are not formally part of the militia (and would be terribly offended if you said they were), they do function the same way: young nobles "volunteer" for fifty years of service in the Royal Army, and can also be called upon to fight as for their lieges at any time afterward.
The professional forces each have their idiosyncracies and unique formations, so we'll mostly be talking about the militia.
The smallest building block is the squad, consisting of ten elves. Typically squads do not deploy and maneuver in battle on their own, this is more for administrative purposes and out-of-combat tasks: every squad has their own tent and donkey cart for their supplies. It's not impossible that they might be sent out for some low-level combat mission like a patrol or so on, but more often individual squads are sent out for things like foraging firewood, digging latrines, erecting fortifications and so on. Whichever soldier has served for the longest has seniority and thus command over the squad, while in reserve units the squad elects a leader (superior officers can also appoint a squad leader if it becomes an issue).
Above squads are companies, composed of five squads for fifty elves in total. Each company is led by a Sentinel for the Spearmen or a Hawkeye for the Archers, a veteran professional soldier who decided to keep serving after their fifty-year tour of duty was over. They also hold the rank of Captain, when it's necessary to refer to them together, rather than specifying their combat arm. In reserve units, their jobs during peacetime are to guard the militia armouries and muster points, as well as organizing practice drills and weapon training for a certain amount of times every year to maintain the skills of their troops. Companies are fully capable of maneuvering independently in battle, with their own standards and musicians, though in larger battles they may be expected to stay in formation with the rest of the regiment.
Above companies are regiments, composed of ten companies for five hundred elves total. Regiments are the largest single combat arm formation: in large battles you'll see entire regiments of Spearmen and Archers maneuvering around as one, though they can also break down into companies or detach them off for specific tasks or as part of task forces. For an example, an outpost might be garrisoned by a regiment of Spearmen and a regiment of Archers, and send out a force consisting of a company of each combat arm to patrol the surrounding area. Regiments are led by Commanders, which can be Captains promoted up the chain of command, but this typically tends to be the ceiling for commonborn military careers, and where nobleborn officer careers begin.
After doing their own fifty-year stint in the Silver Helms (Or they can volunteer into the militia if they can't afford a horse and the weapons and armour of a knight, but this is seen as shameful) nobles can be employed in the Royal Army as officers, starting out as Commanders, which is not an uncommon career track for young nobles: their parents might be around for many centuries yet, and while they've seen combat in the Silver Helms a noble is expected to also lead his people into war. This is also where that whole Intrigue At Court thing comes in, because of politics. Obviously every noble is trained on military tactics and how to lead, and they must be fifty-year veterans to receive a command, and if they're obviously unfit they can be turned away, but it does happen that a Prince might call in some favours and pull some strings to get his son or daughter a field command ahead of more deserving candidates. They're rarely outright incompetent, just not necessarily the best person for the job. Reserve regiments are led by the local minor nobles from whose fiefs they are mustered (indeed the local nobles are the ones who have the legal authority to mobilize these regiments, and sending young nobles to serve as officers in the Royal Army is meant to prepare them for that moment.)
Active-duty regiments also always have at least one Battlemage attached to them who functions as the Commander's advisor and second in command- they may and often do attach more than one Mage depending on availability, but always at least one Battlemage. Reserve regiments obviously cannot guarantee having a Battlemage on hand (except in Saphery), but if they are kept mobilized for long periods it is part of elven military doctrine to attach one as soon as possible.
Above regiments there are legions, consisting of five regiments of Spearmen and five regiments of Archers, for five thousand elves. In addition, each Legion has an artillery train of ten batteries (each made up of ten crews) of Eagle Claw Bolt Throwers, and similar to regiments legions always have an attached Archmage who fulfills a similar function. Legions are led by Generals (Or in reserve legions, Princes), and are the largest permanent organizational unit used by the Asur: if multiple legions are required to work together, seniority of command is determined by a complex system of comparing prestige, noble pedigree, record of service, court favour, tradition, titles or at the end of the day appointment by the king or ruling prince. Legions also in practice never deploy alone: while they are not a permanent part of the legion (and indeed the specific regiments may change over time or between campaigns) the Asur never send a legion to war without attaching two regiments of Silver Helms (Composed of ten squadrons of fifty knights) to it, unless the situation is desperate.
Thus we get the standard Asur field army: 2,500 Spearmen, 2,500 Archers, 1,000 Silver Helms, 100 Eagle Claws, 10 Battlemages and 1 Archmage, not counting various support personnel. Of course, again in practice the Asur almost never go to war like this, the legion only forms the core of the army into which various additional units are bolted as needed and available: various religious and secular warrior-orders, household retinues of the nobility, stray regiments of Spearmen, Archers and Silver Helms, kingdom-unique forces such as chariots or Mistwalkers or Shadow Warriors and so on. Reserve legions in particular are prone to variation: An "Ellyrian Legion" consists of four regiments each of Spearmen and Archers but has six attached regiments of cavalry while Nagarythe almost never fields full legions because it just doesn't have the population for it, and so on. And of course units are understrength all the time.
Regiments and legions also have their own symbols, colours and names: names like the Revenants of Khaine, the Fangs of Chrace or the Flameblades are etched into Ulthuan's history, and the elves are very proud of them. Reserve units are no less prestigious for that they are only mustered in times of crisis, as while the active-duty units are considered to represent all of Ulthuan and her colonies, the reserve units carry the pride of their home kingdoms.
Lastly, allow me to illustrate how the system works with an example from Fanriel's past: the Battle of the Wailing Fen. High Prince Moranion received word of a daemonic army marching towards Tor Yvresse, so he called upon his vassals to muster their forces. He raised two legions from his own fief in and around Tor Yvresse, the Watchkeepers and the First Yvresse Guard. Four more legions arrived by ship from his vassal Princes: the Second Yvresse Guard, the Cairnwalkers, the Eastwardens and the Fifth Yvresse Guard from Elessaeli, Cairn Thel, Sardenath and Cairn Lothel, respectively. This wasn't the full strength of Yvresse, these were forces drawn from port cities that could make it to the fight before the daemons reached Tor Yvresse, and Moranion didn't want to gamble his kingdom on one battle.
Each of his vassal Princes also brought with them the customary two regiments of Silver Helms, and Prince Arhalien of Cairn Lothel brought four. Prince Elonaer of Sardenath and Princess Urandrille of Elessaeli brought a regiment of their own retinues, while Princess Fanriel of Cairn Thel brought a force of some one hundred Swordmasters of Hoeth, leaving the Drangleic household troops to guard Cairn Thel.
In addition to this, Princess Landril of Tor Andar brought three regiments of Cothiquean Waveriders, the Knights of Tor Gaval sent a mixed force of aerial cavalry, and Phoenix King Finubar sent six regiments of Sea Guard and a regiment of White Lions. Lastly, Moranion decided to leave the Spire Guard of Tor Yvresse to defend the city, but brought with him four regiments of Silverin Guard, the Sentinels of Astaril (an overstrength regiment) and a Circle (a loose unit denoting a force of unattached Mages) of Wardmakers.
Moranion obviously had overall command as the ruling prince of Yvresse, and also formally took command of the Watchkeepers, as tradition dictates that the Warden of Yvresse must. However, he also anticipated that he would have to personally take on An'ggrath, the Bloodthirster leading the daemonic army, and named his younger son Prince Argalen as his deputy for the Watchkeepers. He then put his elder son Eltharion in charge of the First Yvresse Guard, whilst Princess Fanriel, Princess Urandrille and Prince Elonaer led the Cairnwalkers, the Second Yvresse Guard and the Eastwardens, respectively, while Prince Arhalien delegated the Fifth Yvresse Guard to his cousin Prince Malonir, as he was appointed by Moranion to lead the combined Silver Helms.
Moranion then assigned Landoril to skirmish before the lines met and draw off daemons into an ambush by Arhalien's Silver Helms, and subdivided his main force into three wings. He put Eltharion in charge of the left flank and assigned the Fifth Yvresse Guard under him: he wanted to give Eltharion additional command experience, but the heads of the princely houses would protest being subordinated to someone who was only heir. By giving Arhalien command of the cavalry he ensured that there would be a legion not led by the head of a house, thus allowing him to place them under Eltharion and Eltharion in charge of the left flank, without causing an issue with his vassals. He placed Princess Fanriel on charge of the right flank, as she was learned in warfare at the White Tower, but Cairn Thel and Elessaeli are neighbours and rivals so he couldn't put Urandrille under her. Instead he placed the Second Yvresse Guard at the center, nominally under him but once he engaged An'ggrath seniority would fall to Urandrille over Argalen, salving her pride as she got to command the prestigious center for a good part of the battle. Prince Elonaer was young and inexperienced, so there were no complaints when Moranion put him under Fanriel. Finally, he placed his most elite troops in the Silverin Guard, White Lions and Knights of Tor Gaval to reinforce the center where they would be most needed, Eltharion's own personal unit in the Sentinels of Astaril at the left flank, and the Sea Guard with Fanriel on the right, reasoning that she needed additional troops to compensate for Prince Elonaer's inexperience as a commander.
