Mount&Blade/Rhodoks

The Rhodoks are an unusual faction; whereas the Khergits are cavalry-focussed the Rhodoks have only infantry and crossbowmen. Their spearmen have a combat advantage against cavalry but are only moderately useful against other infantry.

Against infantry
The individual Rhodok infantrymen is a poor fighter, a large band of them in tight formation is a different story all together. Though it may be preferable to have your crossbowman bombard the enemy to kingdom come, if you need to engage in melee, have your Rhodok infantry advance as a large mass where the reach of their spears can cover each others backs and deliver pointy death to their enemies.

Against cavalry
If you have a mixed array of rhodock troops, then the best thing to do is to order your infantry ahead of your crossbwman, on a hill this works much better, and as the cavalry approach, they will be knocked down by the heavy fire of crossbow bolts. Meanwhile, your rhodock infantry will have a very good chance in taking down the infantry without a problem, unless of course you are fighting a bunch of hired blades, with only a handful of spearmen.

Against archers
Archers are the bane of infantry and should be dealt with quickly. If engaging archers on flat ground have your crossbowman spread out and charge in. They will advance from the front and provide covering fire whilst drawing the barrage from the enemy archers.

Have your spearmen and sergeants pack themselves in a tight formation and move from the sides to outflank the archers either from the sides or the rear.

If engaging archers on uneven and mountainous terrain, the best thing to do is to lure them to you. Bowmen may fire faster but this also means they run out of ammunition quicker. Have your troops hide in a sheltered location and ride out to distract and draw their fire. Once their ammunition is used up they should make easy prey for your men.