Birthright Military
Building an Army
Soldiers can be acquired in five ways: musters, levies, mercenaries, allies and holdings.
Mustering Troops
Mustering is the easiest; the Regent simply spends money to raise an army from his subjects. This has costs associated with it, and is not always convenient - few Provinces have the resources of muster up an entire unit of knights, for example. A Province cannot muster more units in a domain turn than it has Levels - so a Level 3 Province can only muster 3 units of troops per domain turn. Once an army is mustered, it must be outfitted, trained and organised, and cannot be used in the same domain turn it was mustered in.
Raising Levies
Rulers of a Province can also raise levies. Levies are ineffective compared to professional armies, but they come with significant advantages. Levies cost nothing to muster, and for the first three months they have no maintenance costs. However, once mustered and disbanded, they cannot be raised again for 12 months. Furthermore, as levies are ordinary people with trades and livelihoods, raising levies reduces the Level of a Province by 1 temporarily. If they are defeated on home soil or are disbanded, the Province is restored. If they are defeated and disbanded on foreign soil, the Province's Level is permanently reduced. Each Province can produce a number of units equal to that Province's Level - a Level 3 Province will produce 3 units of levies.
Mercenaries
Mercenaries can be hired by any character who has enough money. Even non-Regents can become great mercenary captains. This makes them particularly convenient for Regents who do not have much territory to muster from or who need to supplement their forces with a large number of troops on short notice. Unlike normal troops, mercenaries are ready to be deployed the moment they are hired - there is no waiting for training or outfitting. However, mercenaries are notoriously unreliable - if a mercenary unit is defeated in battle, it immediately disbands. Furthermore, mercenary bands that are not paid are likely to turn to brigandry, becoming a problem in their own right.
Allies & Holdings
Allies are troops loaned by one ruler or another through diplomacy. They usually remain under the control of their own Regent, who must enter the battle or assign a lieutenant to command the armies.
As noted under the Fortify action, fortified Holdings and castles are garrisoned with 10 men per level of the Holding/castle. These soldiers can be ordered away, but this effectively neutralises the fortification until they return.
Unit Types
Unless otherwise noted, a unit is generally about 200 footsoldiers or 50 cavalry. All costs are given in gold bars.
Basic Units
| Unit | Base Move | Muster Cost | Maintenance Cost | Required Level |
| Archers | 2 | 2 | 1 | P(2)/G(4)/T(4)/L(4) |
| Artillerists | 1 | 4 | 2 | P(5) |
| Cavalry | 3 | 4 | 2 | P(3) |
| Infantry | 1 | 2 | 1 | P(1)/G(4)/T(4)/L(4) |
| Infantry, Elite | 1 | 4 | 2 | P(3) |
| Irregulars | 2 | 1 | 1 | P(1)/G(3)/T(3)/L(3) |
| Knights | 2 | 6 | 2 | P(4) |
| Levies | 1 | 0 | 1 | P(1) |
| Merc Cavalry | 3 | 6 | 2 | Any |
| Merc Infantry | 1 | 4 | 2 | Any |
| Merc Archers | 2 | 4 | 2 | Any |
| Merc Pikemen | 1 | 4 | 2 | Any |
| Merc Irregulars | 2 | 3 | 1 | Any |
| Pikemen | 1 | 2 | 1 | P(2)/G(4)/T(4)/L(4) |
| Scouts | 3 | 2 | 1 | P(0)/G(2)/T(2)/L(2) |
Archers are longbowmen equipped with padded or leather armor. Longbowmen usually carry a large weapon such as a battle axe or morning star when engaged for war, but at other times they may only be equipped with a short blade to keep their load light.
Artillerists are special units used to operate siege machinery and to attack castles and fortified holdings. Castles and fortified holdings cannot be attacked without artillerists. This unit is useless unless attacking from pre-prepared positions.
Cavalry ride light or medium warhorses, wear chain mail or brigandine armor, and fight with the sword, lance or crossbow. Used to engage light troops and to harry enemy positions with their mobility.
Infantry are rank and file footsoldiers, most effective against archers and pikes. They are ineffective against mounted troops in an open field. Usually wear light to medium armor and wield large weapons such as halberds, two-handed swords, and battle-axes. Elite Infantry are equipped with splint, banded or plate mail, and usually fight with weapon and shield. They are capable of enduring anything short of a heavy mounted charge.
Irregulars are barbarians, skirmishers, marauders, and so on.
Knights are elite cavalry, consisting of both the knights themselves as well as their squires and men-at-arms. Armed in plate mail at the very least and mounted on heavy warhorses, only archers and pikemen are their enemies.
Levies are the weakest, most poorly trained and equipped soldiers. Callous commanders use them as ballista fodder; strategic commanders use them for home defense or protection of supply lines, freeing professional soldiers to fight on the front lines.
Pikemen, along with archers, are a response to the dominance of knights on the battlefield. They form a dense hedge of spear points that resists a mounted charge and can also strike an enemy line with unstoppable force, making them effective shock troops. They have their disadvantages, however: they are easy targets for archers, and in pitched battle their unwieldy pikes are outmatched by traditional infantry.
Scouts act as skirmishers and infiltrators on the battlefield, but are most useful outside of it. An army with a company of scouts automatically identifies enemy units in the same and adjacent Provinces, making it easier to avoid strong forces and make contact with weaker ones.
Special Units
| Unit | Base Move | Muster Cost | Maintenance Cost | Required Province |
| Dwarf Infantry, Elite | 1 | 4 | 2 | P(4) Dwarven* |
| Dwarf Crossbows | 1 | 4 | 2 | P(4) Dwarven* |
| Elf Archers | 2 | 4 | 1 | P(3) Elvish |
| Elf Cavalry | 4 | 8 | 2 | P(4) Elvish |
| Goblin Archers | 1 | 1 | 1 | P(2) Goblin* |
| Goblin Irregulars | 1 | 1 | 1 | P(1) Goblin* |
| Goblinoid Infantry | 1 | 2 | 1 | P(2) Goblin* |
| Goblin Cavalry | 2 | 4 | 2 | P(3) Goblin* |
| Gnoll Marauders | 2 | 2 | 1 | P(1) Gnoll* |
| Gnoll Infantry | 1 | 3 | 1 | P(2) Gnoll* |
Special units are those that are unique to a certain group or nonhuman race. Those marked with an asterisk (*) in the requirements can be hired as mercenaries even if you do not meet the requirements to muster them. Note that you don't necessarily need to be, for example, a gnollish Regent, to hire gnolls. If your Province contains a large area infested by gnolls, it may be possible to muster gnollish troops if your relations with them are good enough (this is where Diplomacy actions are useful). Likewise, if your Province includes a dwarven mountainhome, you can muster dwarven troops - as long as the dwarves are willing to fight for a human.
Dwarves are armored heavily in the finest plate armor, and their weapons are of the finest possible quality. They are famous for their unshakable morale and implacable discipline. Dwarves move through mountains with a reduced movement penalty.
Elves are peerless archers, and their cavalry is the swiftest and most deadly on Leng. They can move through forests with no movement penalty.
Goblins fight with viciousness and sheer numbers, but have poor morale. Goblin cavalry ride wargs. Goblins only form irregular units, but hobgoblins or orcs can form infantry units. Hobgoblin soldiers are difficult to come by, but have good morale even compared to human infantry due to their brutal and autocratic society. Hobgoblins are particularly good at keeping cowardly goblins in line. Orc infantry are functionally identical to hobgoblins, but without the morale and discipline. They do tend to be easier to find, however, and their presence does improve the morale of goblin troops.
Gnolls are unruly and have poor discipline, but are physically powerful and stand 7 feet tall. They move through hills with no penalty.
Troop Movement
As noted under the description of the Declare War and Move Troops actions, the movement of troops is divided up into War Moves. A War Move lasts one week, and the Declare War and Move Troops actions both grant four War Moves - i.e. a month's worth of troop movement. In one War Move, a Regent can move each of his units as much as their movement speed allows them to. For example, archers have a movement speed of 2, so they can travel 2 Provinces in a single War Move.
Movement speed is also modified by the type of terrain being crossed. For example, desert has a terrain movement cost of 2, meaning it takes twice as long to cross desert as other types of terrain. A unit of archers could only travel across 1 Province of desert in a single War Move. If a unit doesn't have enough movement to cross an entire Province in a war move, they can travel into it on one move and out of it on another. A full list of terrain types and their associated movement costs can be found on the main Birthright page.
Moving troops is not free: it costs money, at a rate of 1 GB per 10 unit-provinces in friendly territory, or 1 GB per 5 unit-provinces in hostile territory.
Castles
Building a castle in a Province is a good way to tie up enemy troops. Castles force any enemy unit that enters a Province to stop immediately. Enemy units cannot pass through a Province fortified with a castle - they must stop or go back the way they came. In order to neutralise a castle, you must put as many troops as are in the castle's garrison in the Province, plus one unit for each level of the castle. Once you do this, the castle is considered to be under siege. While a castle is under siege, it drops by one level in each domain turn. If the number of occupiers ever drops below the number needed to neutralise the castle, however, it immediately returns to its original level. If a castle drops to level 0, it is destroyed by starvation, disease, etc.
The other way to attack a castle is by assault. This requires you to have units of artillerists in your army, and involves the construction of siege equipment and the storming of the castle.
Battle & Reconnaissance
At all times, Regents know what units are within their own Provinces. A Regent can also use the Espionage action to discover troop movements and locations in the domains of other rulers. Likewise, armies usually are only aware of the locations of hostile troops in the same Province as them, but if they have a unit of scouts they can obtain additional information about enemy units in adjacent Provinces.
When an army moves into a Province that contains native units or Holdings, the defenders must decide whether to stand their ground or retreat. It is not possible for defenders and attackers in the same Province to simply "not fight". A hostile army occupies a Province when it enters, and is impossible to simply ignore. In some cases, a very small army (1 unit or less) that is passing directly through a Province on its way to somewhere else might not be considered to be occupiers, but this is the exception rather than the rule.
The actual determination of the battle itself is not within the scope of these rules. It depends on many factors - the units, the terrain, the leaders, and so on - that are best determined by other wargaming systems.