Heavy Infantry has a baseline movement speed of 6 tiles in open terrain. The purpose for these guys are to a) take damage and b) inflict damage. They excel at absorbing attacks and they are incredibly useful given their amazing blocking and covering bonuses. Heavies are basically the backbone of your army!
The fighter class is the base heavy class, and he can get the Guardian tree – a nice 25% defense bonus. He has high armor, strength, and HP. The fighter can change into almost any class, which makes him very diverse.
The Soldier is pretty much the same as a fighter, just a little stronger. The Soldier can then change into four classes.
The Zweihander is highly specialized infantry that attacks in a wide-arc, striking the units adjacent to it in the same row. Each attack hits an entire row in a splash damage type style (secondary units get hit at about half power).
The Champion is probably the purest muscle class – he walks up and hits you twice. The Sentinel, on the other hand, still has the Guardian tree and he hits with a pole arm. They are defensive powerhouses – huge armour and HP increases.
They have an advantage against cavalry, plus a phalanx bonus when near other spearman. They can upgrade to Sentinel (see above).
You do not get a big power boost going to Samurai, however you acquire a bow, which makes the unit very useful. Counter attacking at range plus having the tankiness of heavy infantry is awesome.
Another high powered Polearm unit, his attacks strike the units behind the target. He’s got a huge spear, and he’s great at hitting units in the back rows.
The basic heavy Cavalry. They are similar to heavy infantry, but they have a horse, and obviously get better movement.
The Knight is an upgraded version of the Cavalier. Knights are beefy, reliable, and can even defend against archers.