Aeneid Book XII

At the end of the Aeneus' rampage (perhaps aristeia is a more appropriate term), I have to wonder if Turnus really had to die. If he had not carried Pallas' belt around like a trophy, Aeneus would have shown him mercy. In Fagles' translation, we see that Turnus' pleas for mercy "began to sway him more and more" (Book XII, lines 1096-7). In Fitzgerald's translation, Turnus' words "began to bring [Aeneus] round from indecision" (Book XII, line 202-3). The sight of the belt "flaunted" by Pallas' enemy was too much, so Aeneus strikes Turnus down. But by defeating Turnus in such a manner was Aeneus putting his own interests before the interests of the Roman state? Throughout the Aeneid, we see Aeneus putting the public's interests before his own. Keeping a strong warrior like Turnus around could have been a real boon to New Troy or Rome, but would Turnus' survival have been a threat to Aeneus and Rome? I must admit it has been some time since I took Western Civilization 1; I don't really remember too much about ancient Rome, but I doubt a Caesar would have allowed an enemy to remain alive. Also, Aeneus becomes the Achilles in the Iliad completely after Turnus has been killed by his hands.