After the siege, the Durhua Empire is formed, conquering a few Nord cities (and thus leaving the nords extremely weak) and declaring war to anyone except the Swadians. Also, I get it you're fighting the siege as the attacker with the dark army? If you have a bow, try to take out the enemy archers. They are a great danger, as your ammo is refilled every few minutes as a siege defender. When I fought against the Dark Army, I simply stood in one spot, blasting arrows, and killed about 300 of the ca 900 attackers. So focus on the archers, for the rest, you should do it, because your dark army is just so much bigger.
