Swordsmen... I use them for a countercharge... I prefer Vikings and Billmen. Vikings and billmen get armour piercing, they are a great counter against swordsmen.

However swordsmen are good once the spearmen have received a charge from cav you flank with the swordsmen.

Also if you don't have any swordsmen, vikings or billmen you will find it hard going against an army with a lot of swordsmen if you are spearmen heavy.

Combined arms are always good.