[Ironhawk]

Yeah you seriously need to change your strategy, gar. If you are seiging a fort for more than like 4-5 turns you are doing something wrong. You still havent listed how many enemy units you are facing off against so, it probably is something comparable to you (which will take a loooong time) or more than you (which will *literally never* work).

As suggested above you need to bolster your army with a couple of things:

1) Fewer, Stronger units (think giants)
2) Supply Items and/or units that do not eat
3) Seige Items

You can recruit some of the units in question but likely you will have to summon them and of course you will need to forge the items. No nation was listed so here are a couple of paths that are handy when seiging - if you nation has them, give them a shot:

Nature: Vine Ogres (high str, NNE), Wineskins
Earth: Seige Golems!, Gate Cleavers!
Air: anything that flies, Horn of Blasting (or whichever the air siege item is)
Death: tons of undead



Alternative Strategy:
If you are truly desperate you can just throw ALL your men at the castle and just accept that they will starve. So let them! Barring the weakness affliction they will still seige at full strength until they die. Once you break the walls, just leave enough men to counter the defenders while you move out the rest of the starving and move in your fresh troops for the Fort Storm attempt.