Unlike Rise of Kings: Chronicles, where the Outpost trains Mercenaries, not all Mercenaries in Warbirth can be recruited from the Sentry Post. Some require special buildings like 0AD's Carthaginian civ in order to be recruited.
- 1 Units trained
- 1.1 Mercenary Quarters
- 1.2 House of Worship
- 1.3 Mercenary Quarters
- 1.4 Fort
Mercenaries unlike Rise of Kings are not knockoffs of other factions' units: instead they are an additional low-grade unit that can be amassed quickly with sufficient money on hand. If you have cash it is better to recruit the mercenaries rather than your own which require two resources and more time, instead of just one.
Clad in skins and unbound hair. Trained by Zhou and Shang. Xirong are most likely to be javelineers, archers and horsemen and seem to be related to prehistoric Tibetans.
- Xirong Skirmishers
- Xirong Archers
- Xirong Horse Raiders
Xirong tend like Scythians to have good LOS.
A different sort of barbarian, but more sophisticated and only available late-game. Available only to Bach Viet and Zhou.
- Man Warriors (they fight as heavy infantry) 
- Man Rangers (they fight as archer cav) 
- Sino-Man Crossbowman 
They appear to be spearmen, swordsmen and javelineers, and are usually associated with Egyptians .... although it might be possible to have the Tartessians train them too.
- Libyan Skirmishers 
- Libyan Spearmen 
- Libyan Swordsmen 
Trainable, usually for Hebrews and Babylonians
- Mercenary camel cavalry  and
- Arab mercenary clubmen 
- Arab mercenary skirmishers 
- Mercenary camel archers 
Arabs sacrifice hitpoints for greater movement speed.
Guti are mostly skirmishers and bowmen, and have the ability of running faster than other factions' archers and javelineers. They probably upgrade to other units. Just which ones?
- Gutian Skirmishers 
- Gutian Bowmen  => Composite Bowmen
- Gutian Spearmen  => Heavy Spearmen
- Gutian Berserkers 
Guti are usually recruitable only to Elam and Babylon. They are basic units, who are cheap but weak although the Berserkers clearly do more damage to buildings and light units by virtue of being axe units.
House of Worship
Influence replaces the ramp costs of these units.
Essentially spearmen, clubmen and bowmen recruited from non-Aryan tribes in India. No ramp cost, but no LOS either. They are still good jungle warfare experts.
- Jungle Spearmen 
- Jungle Clubmen 
- Jungle Bowmen 
- Jungle Hunters 
These should be trainable to Bach Viet, Nubians, Zhou and Indians.
Hyksos, I suppose. The are bound to consist of:
- Semitic Axe Levies
- Semitic Spear Levy
- Semitic Skirmisher Levy
- Semitic Battle-Chief (a light chariot)
Most lilkely candidates are Phoenicians and Egyptians and Hebrews.
- European Spearmen
- European Slingers
- European Archers
- European Hurlers
Used mostly by Rasenna, Celts, Thracians and Germans.
Hurrians are known for their cavalry and their spearmen, who are all lightly armoured. Hurrian scouts, while nothing special, are markedly faster to build like most mercenaries. Hurrians appear to be accessible to the Mitanni, Elamites, Lydians and Babylon.
- Hurrian Spearmen
- Hurrian Heavy Spearmen
- Hurrian Warlord (light charioteer)
Greek units are some of the best units. Strong and disciplined heavy spearmen.
- Mistophor Archigos (light melee chariot)
- Mistophor Spearman (Myceanean)
- Mistophor Noble Spearman (Mycenaean long pike)
- Mistophor Hoplite (an upgrade that replaces both the Spearmen and Noble Spearmen)
See the Sea Peoples. Used mostly by Tartessian, Egyptian, Argives and Rasenna.
- Pirate Raiders
- Italic Spearmen
- Italic Archers
- Pirate Chieftains (swordsmen)
These units are known to have some leather armour and good weapons. Good turn speed, excellent rate of attack. Very expensive units, but what you see is what you get.
- Renegade Chinese Warlord
- Renegade Chinese Footmen (Ge-armed)
Food is necessary for the ramp of these units.
They sacrifice armour for attack, and are based off Hittites. Understandably they appear in Lydian, Mitanni and Hittite armies.
- Anatolian Shepherds 
- Anatolian Spearmen 
- Anatolian Axemen 
- Anatolian Warchief 
Described as being clothed in skins and feathers. Trained by Zhou and Koreans. Most likely to be skirmishers, bowmen, crossbowmen and Spearmen.
- Beidi Spearmen
- Beidi Raiders
- Beidi Bowmen?
- Beidi Crossbowmen
Cimmerians are based off the Thracians, and can be found as mercenaries for Babylon and Assur.
- Cimmerian Axemen
- Cimmerian Hurlers
- Cimmerian Horsemen
- Cimmerian Renegade Noble (light charioteer, possibly melee)
Little is known about these people although it is suggested that Andronov style costume be used for them.
- Balkan horsemen, along with
- Balkan skirmishers,
- Balkan axemen and
- Balkan clubmen
These units are common for the Phrygians and Lydians.
Scythians are mostly horse-riding warriors. Ultimately the best ones, but they carry far less armour than mainstream Iranian units. By far and large, Scythians are available to many Near Eastern factions, particularly:
Scythian mercenaries include:
- Scythian Bowmen
- Scythian Warriors (armed with axes)
- Scythian Light Lancers
- Scythian Horse Archers
- Scythian Renegade Noble (axe cavalry)
KAssite units are mostly low-grade, being slingers and axemen, being trained faster than normal axemen or skirmishers. They eventually upgrade to other units. Kassites appear to be accessible solely to Elam and Babylon. Like many Near Eastern units they are dressed in Neo-Sumerian, pre-Iron Age style. They carry either round shields or square wicker shields.
- Kassite Slingers
- Kassite Axemen
- Kassite Swordsmen