You decide to attack! Just before dawn you lay down a fierce barrage on the fort from your cannons. While this is going on, you feint to the west with some of you men, but you send 1,000 troops towards the northeast corner. After a fierce fight, your troops just manage to get inside the Fort where they are beaten off by a desperate last stand of the forts garrison.
Good effort. There is probably not much more you can do given your limited resources.