That's the main problem for the European army when they face the eastern (MED2 have the same problem too)


There're some ways to prevent it
Force them in "Urban warfare". Focus to attack their cities. Make fort when you want to face them. They will try to attack it (you lose some man when under siege but you can win). If not abandon the fort and they will take it. Now it's your turn to siege them.
If you have to face them on the open. Deploy your troop in the corner of the map to tired out Cataphract (they tire event when moving). Deploy their also eliminate both ranks and make your line more solid to face the incoming charge. Try to quickly pocket them when they charge. Just remember to bring some archers to take out their HA and hope they don't have too much cataphract archer who will crush you in both fire power and melee
