I think there should be self-counter units for each class, that are good for massing against their own class, but are somewhat less effective against everything else. There should also be some neutral relationships, where a unit neither counters nor is countered by another unit. Here's a short draft of a possible set of counters: Melee Infantry: Spearmen are anti-cavalry. Strong attack against cavalry but somewhat weak armour.Swordsmen are an infantry self-counter. Medium-powered attack and strong armour for taking out other infantry.Ranged Infantry: Archers are anti-infantry. Good damage for picking off infantry but weak armour that offers little protection when put into a melee battle. Vulnerable against melee cavalry that can close in quickly.Skirmishers are a ranged self-counter. Even weaker melee armour than the archer but strong-ish ranged armour, which makes the unit more effective when massed. Should be able to take out an equal group of archers without suffering too much damage. Also has weaker attack so not effective against melee infantry.Slingers should be considered as light siege units. They still have the same weaknesses as other ranged infantry, but are slower firing, higher damage, and reasonably effective against buildings in the midgame where proper siege units aren't available. They should be quite inaccurate to make them ineffective against cavalry or small squads of units.Melee Cavalry: Sword Cavalry are anti-ranged. Not quite as strong (armour & attack) as its infantry counterpart. Instead uses its speed to be a counter against infantry archers and skirmishers.Spear Cavalry are a cavalry self-counter. Higher damage against cavalry and weaker armour than its infantry counterpart.Ranged Cavalry are an interesting interruption in an otherwise nice balance cycle. Archer Cavalry are a more mobile version of the archer. Slightly less powerful than its infantry version but has increased mobility that allows it to escape melee units.Skirmisher Cavalry are a more mobile version of the skirmisher. Slightly less powerful than its infantry version but has increased mobility to escape melee units or chase down cavalry archers.A few additional notes on some relationships between units. Swordsman vs Archer: Swordsmen will destroy archers if they get within melee range, but otherwise will be picked off as any other infantry. Should not counter either way.Cavalry Swordsman vs Cavalry Archer: Same as above.Cavalry Spearman vs Cavalry Archer: Same as above.Cavalry Skirmisher vs Infantry (except skirmishers): Will win purely because the infantry won't be able to get close enough. Should not counter either way.Cavalry units should always be beaten by their infantry counterpart, but not by a wide margin. They should be a bit weaker (attack & armour), because they make up for it in mobility.Edit: Maybe the role of Skimishers and Archers should be switched, and the archer given a range bonus to provide a more sensible and strategic counter.