Siege until the enemies die starving is real warfare tactics.... And you MUST siege them until dead if you only have HA's in your army (playing as the nomads)... Casse is better, they can order their men to use the Ram and Ladders.... Steppe infantry is useless...

Anyway, when playing Casse, after get 3 or 4 settlements with starving siege... you just need to pump out swordsmen...