Greek Units
Peasant
The last option of any desperate army (except perhaps slaves or convicts), peasants are good for increasing your numbers...and not much else. Poorly armed and with little military experience, their morale and discipline are both understandably low. They are cheap to train, however, and their one advantage is an ability to hide well. Peasants should be used as an absolute last resort, or in cases where funds are extremely short.
Peltasts
The Greek equivalent of skirmishers, peltasts carry a bunch of javelins into battle. They are also armed with swords and shields, but their lack of armour makes them as weak at close quarters as most other ranged units. They are skilled at hiding and attacking from ambush, but should be drawn back as soon as an actual battle commences.
Archers/Bowmen
Archers were used more widely by some cultures than others. The Romans, amongst almost all the peoples of the ancient world, were prominent in their disdain for archers (and indeed for almost any kind of ranged weapons). Nevertheless, archers are sometimes necessary (particularly, for example, in sieges), and the legions therefore recruited them from amongst the poorer sections of society, and from allies. They are not armoured and thus almost useless in hand-to-hand combat.
Militia Hoplites
Hoplites formed the core of the Greek armies for centuries, with their long spears that stretched out more than a dozen feet in front of them. They almost always fought in phalanxes, presenting an impenetrable wall of iron to their foes. As their name may suggest, militia hoplites are drawn from civilian ranks in times of great need, and therefore cannot be expected to be either skilled or disciplined fighters. However, they can still hold off an enemy for a substantial amount of time, particularly a mounted enemy.
Heavy Peltasts
The Greek equivalent of skirmishers, peltasts carry a bunch of javelins into battle. They are also armed with swords and shields, but their lack of armour makes them as weak at close quarters as most other ranged units. They are skilled at hiding and attacking from ambush, but should be drawn back as soon as an actual battle commences. The heavy peltast is better protected than the ordinary one, and can perform better in battle.
Hoplites
Hoplites formed the core of the Greek armies for centuries, with their long spears that stretched out more than a dozen feet in front of them. They almost always fought in phalanxes, presenting an impenetrable wall of iron to their foes. These hoplites are powerful infantry, although they are vulnerable against the more maneuverable Roman legions. As they must provide their own equipment, they are normally fairly well-off citizens.
Armoured Hoplites
Hoplites formed the core of the Greek armies for centuries, with their long spears that stretched out more than a dozen feet in front of them. They almost always fought in phalanxes, presenting an impenetrable wall of iron to their foes. Armoured hoplites are better protected than others, but operate essentially the same way in battle.
Spartan Hoplites
The rigidly military city-state of Sparta fielded the best infantry in the Ancient world for many years. Babies who appeared weak or sick were left to die; strength and discipline were the only things that mattered in Sparta. These hoplites are even better-trained than the Romans legionnaires, since military prowess is the only thing that matters in their society; however, they have the same weaknesses as other hoplites, specifically a lack of tactical maneuverability.
Militia Cavalry
These light horsemen are armed with javelins and are therefore ideally suited for raids and scouting, but not very useful in a pitched battle. They should definitely be kept away from enemy cavalry, which they have no protection against. Militia cavalry, like militia hoplites, were recruited from civilian ranks only when necessary.
Greek Cavalry
The Greek medium cavalry unit, these cavalry go to war without either shields or armour. They are therefore not very strong against other horsemen, and must also be used more for raids or attacks on ranged units. They are armed with spears. Greek cavalry, as compared to militia cavalry, was a more professional force, with better training and more experience.
General’s Cavalry
A bodyguard was, historically speaking, a functional unit, rather than a type of soldier. In the game, however, they are spear-armed shock cavalry, whose success or failure depends to a large extent on the personal characteristics of the general who they are guarding – his effect on their morale, for example, or on their discipline, will play a large role in determining how they fight. They are in all cases excellent troops.
Incendiary Pigs
This is the unit that everyone has been talking about. The Romans employed groups of pigs, coated in tar and oil and then set on fire, as a sort of primitive artillery. Apart from scaring elephants and horses, they could be useful in disrupting infantry formations. Obviously, the pigs did not survive for very long after being set on fire...
Onagers
An onager, unlike a ballista, worked similarly to a catapult. These machines could be used to hurl projectiles up to half a mile (with the larger versions). The Roman used them in many different ways: large boulders were flung at walls to help bring them down; many smaller rocks were used against enemy troops as a sort of shrapnel; various burning projectiles were used to try and spread fire; and diseased animal carcasses were flung into the enemy-held city to spread disease.
Heavy Onagers
The heavy onager is an enormous catapult built using the same basic design as its sibling and capable of smashing down stone fortifications. It is powered by a twisted bundle of animal sinew ropes, and is slow to wind back and reload. Its missiles are devastating, and it can also fire incendiary firepots. Range is no more than the smaller onager and this makes the heavy onager susceptible to counter fire. Often, it is best employed alongside smaller artillery to deal with enemy fire.
Ballistae
Staple of RTS games, the ballista reappears once more in Rome: Total War. It is much like a giant bow, the bolt being fired due to tension built up in twisted animal sinews. Ballistae can be used to punch holes in walls, or against concentrated enemy troops – although it may be hard to hit men with a projectile that is almost the same size as them.