Scenario Instructions Edit
"Gaul has risen in revolt. You have isolated the great Gallic leader Vercingetorix with only a portion of his forces and driven him into the hilltop fortress at Alesia. He is surrounded, but another great Gallic army is gathering outside your fortifications to free him. Kill the great Gallic leader while avoiding the destruction of your army by the forces inside and outside your fortifications."
- Kill the Gallic leader Vercingetorix. If Caesar dies, the mission will be lost.
Two of the Gauls are outside of your town, and the game suggests that you finish your walls. On the other hand, the outside bases are so small, there is no reason why shouldn't finish the Gauls instead, with your starting army, rather than wasting the stone - so do that. Send your hero, your Legions, and your archers to a base, kill the Villagers and destroy the Town Center, then do the same to the other town.
Now, most of the map belongs to you, and the remaining Gauls are heavily walled in, so you can take your time, if you want to.
Vercingetorix is in a walled-off area at the center of the Gaul camp, so destroy the Towers around him with a Catapult. If you set the Catapult to attacking ground, you can finish off the Horse Archers protecting him, too - they won't think of moving out of the way of the shot if you attack ground.
Since Vercingetorix can't attack at range, and can't get through his own walls, any ranged unit can finish him off at absolutely no risk - you can use your initial archers, if they are still alive, or train a Ballista.