Say, I was going to talk about my idea for the next game here, wasn't I?
Ten unit types exist in the game: Militia, Polearms, Infantry, Heavy Infantry, Ranged, Calvary, Knights, Horse Archers, Siege and Ships. Expect names to be recycled a bit. The last four ranks of Polearms are all Pikemen, but with different adjectives in front of the name.
Militia are weak, cheap and plentiful. The only units that aren't effective against them are Polearms, Infantry and other Militia. Due to the mechanics of the game, Militia work best as meatshields. If a unit can attack several different types of units that it is effective against, then it'll randomly pick one. Therefore Militia can draw attacks away from expensive and hard to replace units like Knights or Heavy Infantry.
Polearms are effective against Calvary and Knights, but get mauled by Infantry, Heavy Infantry and Ranged. They have better defence than attack, and are on the cheap side.
Infantry are rather generic units. Average all around, they are effective against Polearms and Ranged. Weak against Heavy Infantry and Knights.
Heavy Infantry are strong and expensive, and are better on offence than defence. They are effective against Polearms, Infantry and Militia. Only Ranged units are effective against them, so back them up with Infantry or Calvary.
Ranged units have more attack than defence, and are effective against Militia, Polearms, Heavy Infantry and Horse Archers. Infantry, Calvary and Knights can kill them easily though. A mixed force of Polearms and Archers make a nice and balanced force, especially if you include some Knights to kill any Ranged units or Infantry.
Calvary are rather expensive, with okay stats. They're effective against Ranged units, Militia and Horse Archers. Only Polearms are effective against them.
Knights are effective against Militia, Infantry and Ranged units. With their high stats they can smush almost anything else on the field. Polearms and Horse Archers can turn them into mince-meat, so make sure that you bring back up. Needless to say, they cost a small fortune to make.
Horse Archers are rather expensive, and like Ranged units have more attack than defence. They are effective against Militia, Knights and Infantry, but get mauled by Ranged units and Calvary. With their higher attack, they are better at killing Knights than Polearms.
I'm not sure whether to include Siege units in the whole effectiveness table. They're mostly for sieges anyways, and will generally be slightly too expensive to risk in a battle. Plus, they'll have crappy defence.
Hopefully I'll get the conclusion up today, so that we can finally finish the game.