Once i killed the army there i started the siege i noticed that the garrison they had was near but somewhat under the size of the army i had, and very quickly my army started to take attrition, from a lack of supplies i think, as soon as my army size went under the enemies they immediatly gained all the morale they had lost.
So, first off im a new player in CK2 so i decided to do the tutorial before i get into anything and following that i went to war with that small island nation, cant remember the name, as Leon.