This scenario is meant to be played as the attacker.
You have a few more troops than the defender, but frankly, are outclassed.
Victory requires careful use of your few advantages.
Advice: Husband your oil for important catapault shots, and take advantage
of the long range your Tekhir archers have.  And be wary of defender sorties
against both!

        Enjoy,
        Mitch

p.s. As my first effort, I started by modifying the "Spiders" scenario, 
thanks to the author of that.