This is quite a hard map as you need to withstand a few numbers of enemy/AI attacks. Your main objective is to defend the town of Keren. Two more objectives, defending each fort, will summon, but they are optional. Failing them will not keep you from winning as long as you don't lose the town.

You should however, use the forts and the terrain to your advantage. Keeping them in your possession will demand a lot of your tactics and patience, but it is not impossible. You will win when all enemy/AI attacks are repelled.