The secret of using weak units is to combine them in effective ways, with other units, minimising weaknesses and maximising strength. You may have to try to choose suitable battlefield and size of battle to ensure maneuver space.

Any fast unit, can make bait against impetuous troops who tend to attack units they "can beat", and then get tired.

Having the patience to exhaust enemy troops, can change the relative unit strengths hugely, and win otherwise unwinnable battles.