Round table

Let me clarify the question. Suppose I have 20 snipers and 1 troll. The opponent has 3 trolls, a couple of boars, and a bolt unit with 300 damage. In the first battle, with the snipers using bracers, they eliminate 2 trolls, and the opponent eliminates the snipers with the bolt unit. The result is a stalemate: troll vs. troll. Let's assume that both trolls have more defense than attack, so neither troll can defeat the other, even with morale or luck. Then, I load the auto-battle, remove the bracers, and the snipers, with luck, kill all 3 trolls with one shot. Is it fair to finish off the boars, or should I flee from them because I couldn't defeat the opponent in the first battle?