You buy a second Orc hero, give all the troops to Haghesh, and wait a day for reinforcements to arrive from the three dwellings of centaurs. Plus, you build a centaur dwelling in the castle, buy troops there, and in general, Haghesh will have so many archers, including those from the tavern, that the AI will be overwhelmed. Of course, before the battle, you divide the stacks so that the AI's attacks are diverted by a ring of ice, not on the archers, but on the goblins or orcs gathered together. With this setup, victory will be achieved with minimal loss of valuable archers.