Revealing mistake: When the Trojans and Greeks first clash, after Menelaus' death, soldiers wearing kneepads are visible as they fight in the melee. (01:18:25)
Revealing mistake: During their fight in front of Troy's wall, Ajax shoves his weapon into Hector's face, causing Hector to fall back. In the next shot looking up, as Hector hits the ground, part of the wall is gone. There is even a bit of the crew's scaffold, visible behind the edge of the 'stone'. This particular piece of wall was never built as part of the actual set, so when it appears onscreen it is always CG, though in this shot the composite people did not complete it and at this precise angle it should be there. When the bodies are being collected (at the end of this battle), there is a good view of the wall intact. (01:20:00)
Revealing mistake: When Hector and his men are fighting the Greek army outside Troy's walls in the second battle, blood spurts up from the bodies lying on the ground, after "Apollonians! Now!" is shouted. It's very obvious that the blood does not come directly from the bodies. (01:21:25)
Revealing mistake: When the soldiers' bodies are being collected in front of Troy's gate, after the battle, the pattern of the real stone wall (the set) on the left of the gate and all the soldiers that stand atop this wall, delightfully repeats, over and over, on the CG stone wall farther to the left. (01:23:30)
Revealing mistake: In Achilles' tent, while Achilles tells Briseis that she is his guest and not his captive, the distinctive tan lines of the actress' bikini top are clearly visible as Achilles holds her. (01:37:15)
Revealing mistake: At the start of the shot facing Patroclus (dressed as Achilles), as Hector's blade is up against his throat, then slices it, the ridged bottom of the fake latex throat that Garrett Hedlund (Patroclus) wears is visible, when he arches his head back. (01:43:25)
Revealing mistake: When Hector and Achilles stand outside the gates of Troy, they each remove their helmets. As Hector lifts his from the bottom it actually bends, like rubber, in his left hand, though the entire helmet is one solid piece of metal - there is no other material attached. (01:58:05)
Revealing mistake: Many of the spear tips and swords bend like rubber, some at almost a 90° angle and are fine in the following shots! Such as when Achilles' spear tip bends as it makes contact with Hector's shield, once when Achilles does his leap into the air at the start of the duel and then just after slicing Hector's spear with his shield. (Although weapons were made of bronze in those days, and were likely to bend, the fact that the weapons in the film bend to such a degree and then right themselves is impossible.) (01:59:10)
Revealing mistake: When Achilles slices Hector's spear the two wood ends are jagged and the broken spear end that Hector later carries shows a jagged end on the wood. However when Achilles stabs Hector, as the spear protrudes from Hector's shoulder the wood end is perfectly even. (01:59:15 - 02:01:30)
Revealing mistake: Just after Achilles slices Hector's spear, Achilles spins his shield then positions himself behind it. In the next shot facing Achilles, as he starts to walk toward Hector, he does not hold the usual handle on the underside of his shield, instead he holds a small solid handle (used for spinning shield) which is beside the normal handle. Also notice the hilt of the sword is the wrong direction near his elbow, whereas in the following shot when he holds the normal shield handle, the hilt of the sword is properly positioned. (01:59:20)
Revealing mistake: After Hector pulls his sword from his shield, Achilles spins around and pulls his own from the underside of his shield. The sword is unsecured above his hand, not where it should have been, below his left hand on the handle of the shield, which was obviously done deliberately to ready the sword for the shot. (01:59:25)
Revealing mistake: Hector's sword is secured to the underside, from hilt to point, entirely under the shield, perpendicular to the handle he always holds. While Achilles and Hector duel, Hector snaps Achilles' spear with his leg. At the start of the next shot, Hector holds the grip of his sword and pulls it from the shield, above and parallel to the handle, not from where it should have been, obviously deliberately done to ready the sword for the shot. (01:59:25)
Revealing mistake: When the spear handle is protruding from Hector's shoulder, the area of the armor around the circular wound is clearly visible and it is in perfect condition. There is no tear in the armor whatsoever, around the wood, which would have been necessary to allow the wide spear tip to penetrate the armor and actually enter Hector's body as it did. (02:01:20)
Revealing mistake: When Priam kisses Hector's face as the body lies on the pyre, the right side of Hector's face is visible and among the wounds that it sustained while being dragged, the cut under his right eye, which he had while still alive, is conspicuously missing. When the body is viewed from his left, as the flames flicker, the cut above the corner of his left eyebrow, which he also had while still alive, has gone astray as well. (02:14:50)
Revealing mistake: Throughout the entire film, when soldiers are stabbing others it is blatantly obvious in numerous shots that the swords' blades or spear tips don't come anywhere near the armor or skin of the stabbing victim, and the 'victim' usually has either a delayed reaction to their wounds, or react before the weapons ever 'touch' them. (02:20:50)
Revealing mistake: When the Greek's rampage Troy, a Trojan falls through a thatched roof. In the next shot a light haired Trojan male is thrown on top of a black haired male, and are attacked while they lie atop a stone landing. Then at the start of the following close-up, a lone light haired female falls to the ground from that very same stone landing, which is followed by a repeat performance in close-up, by the light haired male of the previous shot, with some differences in this take. (02:21:15)
Revealing mistake: As Hector holds his son, the first warning gong is rung. In the next shot, when Hector hands the baby to Andromache, its small shiny bald head is quite a giveaway that it's really a doll in this shot (not visible on widescreen DVD). Later, Andromache holds her son, Scamandrius, when she finds Helen and Paris, as Troy burns. Aside from the fact that the door hits the back of the baby's head, he now has a bald shiny head, whereas he had hair in previous shots, so it's quite obvious in this shot that the baby is a doll once again. (02:23:05)
Revealing mistake: Paris' arrows have identical black plastic nocks at the end of each shaftment. (02:25:10)
Revealing mistake: After the Greeks break through the palace gates, Paris releases the first arrow into a soldier. As he begins to turn around, the bent dark arrow unbends at his neck at the start of the shot, before it becomes the straight lighter arrow. (02:25:30)
Revealing mistake: After the Greeks break into the palace throne room, there is a close-up and consecutive wide shot of a particular white statue being pulled down with two ropes, then smashes apart on the floor and water. However, in the next shot of Priam, he turns around and as the camera pans out, the very same statue is being pulled down yet again, albeit with very noticeable differences in this take of the same shot. (Each of the unique statues in the throne room is visible in earlier shots.) (02:26:15)
Answer: He was warning the other soldiers that Achilles was coming.