Well, this DOES assume we're going to see something even SIMILAR to medieval/gunpowderless combat, but to fight a battle we need:
1. Skirmish Force
-Wear down the enemy before engagement, cripple poorly-protected enemy units (i.e., unarmored archers, artillery pieces and their crewmen)
+ Archers, missile cavalry, light cavalry
2. Fixing Force
-Once battle is joined, hold the enemy in place. It's preferable if you also break their formation (i.e., use a wedge shaped frontline so the enemy doesn't maintain a good shield wall, and faces inwards rather than outwards).
+ Pikemen or anyone with a shield.
3. Shock Force
-Once the enemy is held in place, flank them with shock units and smash their exposed flanks.
+ Heavy cavalry, sometimes well-armored infantry with two-handed weapons for the faster attack and heavier punch.
Alternatively, we can go straight to "medieval knights" and equip every unit we deploy with full Mithril plate and a polearm or kriegsmesser (Probably misspelled German for "war knife", very shape, very large sword meant to cut through soft armors) of some sort, and let formation sort itself out. Basically, when wearing plate armor, you don't need a shield and you don't need to keep the enemy away from you, you just take the hits (without feeling much of anything) and keep killing.
In this second case, our lineup looks a little more like
1. Skirmish Force
- Same as above
2. Fixing Force
- Did you think you were getting away without regular infantry? These guys basically keep the enemy from overwhelming your primary combatants.
+ Might be spearmen, might be pikemen (pikes preferred), might be just a bunch of guys with munition armor instead of full plate. Either way, they keep the numbers from getting too much in your enemies' favor, basically just holding the enemy in place (if he moves wrong he gets impaled) and letting the knights kill and retire (plate is really, really hot to wear for extended periods of time, and plate-armored soldiers need to back off to rest and cool down in extended engagements)
3. Shock Infantry
- Same as described above
4. Shock Cavalry
- Kind of excessive given what the primary force is, sometimes you might bring lancers, which aren't quite as well-armored as the knights, but still make use of the force of a charge to make it harder for the enemy to fight.
Either way, we're missing non-integrated weaponry for our soldiers, and we're missing mounted shock units (or equivalents). Also, we don't actually have any sort of ranged weapon, just magic that we can't utilize yet.