Book 7 (beginning the Iliadic half) opens with an address to the muse and recounts Aeneas' arrival in Italy and betrothal to Lavinia, daughter of King Latinus. Lavinia had already been promised to Turnus, the king of the Rutulians, who is roused to war by the Fury Allecto, and Amata Lavinia's mother. In Book 8, Aeneas allies with King Evander, who occupies the future site of Rome, and is given new armor and a shield depicting Roman history. Book 9 records an assault by Nisus and Euryalus on the Rutulians, Book 10, the death of Evander's young son Pallas, and 11 the death of the Volscian warrior princess Camilla and the decision to settle the war with a duel between Aeneas and Turnus. The Aeneid ends in Book 12 with the taking of Latinus' city, the death of Amata, and Aeneas' defeat and killing of Turnus, whose pleas for mercy are spurned. The final book ends with the image of Turnus' soul lamenting as it flees to the underworld.
How many years did the war last?