According to Homer's Iliad, there was a time during the war of the Greeks against the Trojans, when Achilles was serioulsy considering to return back to Greece. One day he agreed to allow his friend Patroclus to fight in his place, wearing his armor. The next day Patroclus was killed and stripped of the armor by the Trojan hero Hector, who mistook him for Achilles.
Achilles was overwhelmed with grief for his friend and rage at Hector. His mother obtained magnificent new armor for him from Hephaestus, and he returned to the fighting and killed Hector at a duel. He desecrated the body, dragging it behind his chariot before the walls of Troy, and refused to allow it to receive funeral rites. When Priam, the king of Troy and Hector's father, came secretly into the Greek camp to plead for the body, Achilles finally relented; in one of the most moving scenes of the Iliad, he received Priam graciously and allowed him to take the body away. (find out more about Achilles...)
This relief is picturing exactly the moment Achilles passes with his chariot before the walls of Troy
(seen faintly in the back) holding out the helmet of the defeated Hector who is dragged from his chariot.