Heroes of Mana/Chapter 7: A Farewell Ambush

Take this one slowly and you shouldn't have too many problems. Work your way towards the bridge and build up your forces along the way. Once you have a sizeable force, take a decent group (maybe half of your force) across the bridge, and then lure the enemies back to the rest of your troops. This will isolate Juhani from the reinforcements that come to help him later, and allows you to win without facing all of the enemy's units.