Forts and supply

[Slogan]

Last night I won my first victory. C'tis was trapped in it's Last castle. However, I was never able storm the castle, the prompt said I needed more men. Forty turns and unknown hundreds of troops later his dominion hit zero and I won that way. The wrath of god was going for over thirty turns but evertime I looked at the province it would says, 'this province appears to hold 1680 hostile troops' . What type of castle can hold this many troops?