The Unjust Death of Patroclus

The death of Patroclus is a catalyst for ending the Trojan War because it brings Achilles out of his league of absence from fighting in his quest to avenge the unjust death of Patroclus by Hector. Patroclus was the one closet to Achilles, the one who could reason with him, and when he came to Achilles and begged him to return to the battlefield, Achilles still refused. Achilles' closet companion was not able to convince Achilles to return to battle, but Patroclus was still able to convince Achilles to let him borrow his armor to lead the Myrmidons into battle. Patroclus, wearing Achilles' armor, lifts the moral of the currently loosing Greeks and sends the Trojans running at the sight of Achilles. Even though Hector knows that he is not truly facing Achilles, he still faces Patroclus in battle even after Patroclus' armor is blown off by Apollo and he is wounded by Euphorbus.
Hector goes through a transition throughout the Iliad in that he becomes more and more overconfident the longer Achilles is off the battlefield. Hector starts the Iliad as a sympathetic character, as a loving father, husband, and prince who is just trying to protect his family and city from the onslaught of the Greeks. Hector is overcome with arrogance on the battlefield because he does not have as great of a threat with Achilles no longer fighting and with each Greek Hector kills, he believes he is that much closer to being able to defeat Achilles. Hector is blinded by his victories and truly begins to believe that he could face Achilles and win, with the death of Patroclus being the key moment in which Hector actually believes he could defeat Achilles.
Patroclus and Achilles are not even close to being equal fighters, but Hector still uses the symbolism of defeating "Achilles" as a testament that it would be a fair fight between him and Achilles. Hector decided he defeated "Achilles" fairly and took Achilles' armor as tribute. Even the gods did not approve of Hector's behavior when Zeus says, "[Hector] violated the order of things when [he] took the armor from [Patroclus'] shoulders and head" (17.203-204). Hector had no right to Achilles' armor because he did not even face the true owner of that armor nor did he fight fairly in his battle with Patroclus. Patroclus achieved many victories on the battlefield, including driving the Trojans from the wall and defeating Sarpedon, and Hector only faced him after Apollo blew Patroclus' armor off and Patroclus was wounded. Hector did not deserve Achilles' armor because it was a cowardly and unfair defeat. Hector is sealing his fate with his unjust killing of Patroclus because he is deluded into believing he can face Achilles on the battlefield.