A Barracks is a type of Town Building. It can be constructed in any town belonging to any race, and has no prerequisites. Its base construction cost is 30.
The Barracks serves primarily as a stepping-stone towards unlocking a wide variety of Normal Units for construction. Other buildings, mainly the Smithy and Sawmill, are also required in order to make any of these units available. Together with the Smithy, a Barracks also unlocks construction of the next-tier unit production center: the Armory.
The Barracks has no further effects of its own. It also requires no Upkeep Costs of any kind. If pressed for Gold, a Barracks can be sold back for 10, but only if no other existing Town Buildings in the same town have the Barracks as a prerequisite. If such buildings exist, they must be sold first before selling the Barracks.
A Barracks is simply a large hall which serves to house military personnel - in this case the recruits who will later form Normal Units constructed at a town.
The building is a large rectangular structure, filled with dormitory rooms for the recruits. Many windows line its sides. The top of the structure has a flat roof surrounded with parapets - probably so that it can be used as a defensive fortification in case of attacks (though this has no real effect in-game).
Races and Construction Edit
All Races in the game have access to the Barracks. It is necessary to almost all Normal Unit production, and therefore each race must be able to construct it in order to produce any serious combat units.
A town requires no other Town Buildings in order to create a Barracks - it is available for construction as soon as a town becomes capable of producing anything.
Continuous Effects Edit
Unlocked Town Buildings Edit
A Barracks is one of the two components required for constructing an Armory - providing a place for soldiers to live. The other component is the Smithy, which creates their weapons. The Armory becomes available only once both structures are present in a town.
Unlocked Normal Units Edit
The Barracks itself unlocks no new units for production, since it is only a dormitory for soldiers to sleep in. In order to unlock new units, additional structures must be built - to construct weapons or train animal mounts for these soldiers.
With the Smithy Edit
When a town contains both a Barracks and a Smithy, it can begin to produce Swordsmen. All races have access to their own type of Swordsmen, and thus all races can benefit from having both structures present.
Swordsmen are main-line combat units, and will generally become the most numerous Normal Units in any army by the end of the early portion of the campaign. They are somewhat resilient, and improve well with Experience. They are significantly sturdier against Ranged Attacks than they are in Melee combat. However, they cannot fight effectively against strong units like Fantastic Units or Heroes, at least until they gain plenty of Experience.
The Barracks and Smithy combination does not unlock any racial units.
With the Sawmill Edit
Bowmen are available to the Barbarians, Gnolls, Halflings, High Men, Nomads, Orcs, Beastmen and Draconians. Within their armies, Bowmen provide early-game Ranged Attack capability, which is initially quite poor and useful only against other weak Normal Units. Bowmen however improve well with Experience, and can often cause serious damage to Normal Units once sufficient Experience has been acquired. Until then they are both weak and vulnerable, and will mainly tag along with other armies to gain Experience in combat.
Longbowmen are available only to the High Elf race. They are significantly stronger than Bowmen, and are capable of seriously injuring most enemy Normal Units at a great range. Their accuracy means that they improve very well with Experience, and will generally become very threatening at high levels.
With the Stables Edit
When a town contains both a Barracks and a Stables, it can begin to produce basic Cavalry units, for those races that have access to them. Furthermore, several races can produce non-standard types of cavalry-like units, some of which are significantly stronger.
Basic Cavalry is available to the Barbarians, High Elves, High Men, Orcs and Dark Elves. Cavalry is both fast and strong, but normally relies on its ability to strike the enemy first - killing several enemy figures before they even get the chance to retaliate. This is thanks to the Cavalry's First Strike ability. Cavalry do not last very long in straight-up combat.
The Gnolls produce Wolf Riders instead of normal Cavalry. These units lack the ability of First Strike, but make up for it with greater strength and significantly-faster movement speed. They are used for controlling the battlefield, and are great at killing enemy Ranged Attack units early in the battle.
Horsebowmen and Centaurs, available to the Nomad and Beastmen races respectively, combine fast movement speed with a basic-but-useful Ranged Attack. They can safely move in close to their targets before firing these attacks, thus negating any To Hit penalties usually suffered by other units for firing at a distance. They are, however, less useful in Melee combat.
Doom Drakes are the Draconians' cavalry - but are significantly stronger than any cavalry unit. They are essentially mid-sized, fire-breathing, Flying dragons, capable of causing severe damage to a wide variety of units. They are also very fast, allowing them to easily pick and choose their targets.
With the Animists' Guild Edit
With these two structures present in a Nomad town, this town can produce Rangers. These units possess a respectable Melee Attack and Ranged Attack which they use in tandem. Despite being foot-mobile, they are as fast as horses, and thus can strike rapidly and at close range.
The same two structures in a Beastmen town will unlock the Manticores. These are Flying creatures whose mediocre Melee Attack is accompanied by a powerful Poison Touch attack. They can swoop down on a target with a low Resistance score in an attempt to cause massive damage to it.
The Barracks and Animists' Guild combination does not unlock any standard units.
The Barracks is either directly or or indirectly (via another building that requires one) a required building for almost every military unit in the game; the only units that can be produced without one are Triremes, Galleys, Catapults, Spearmen, Engineers, Settlers, Shamans, Priests, Magicians, and Warlocks. If you don't want to build any unit not on that list, it may be perfectly reasonable to skip the Barracks, and if you change your mind, 30 is hardly a huge barrier. You should have some Towns capable of producing more advanced units, but it's hardly essential to every town.
A Barracks provides no benefits other than the ability to produce more advanced Normal Units, nor do any Town Buildings that require a Barrackss; as such, you should delay building a Barracks until you actually need one.