Continuity mistake: When Paris and Menelaus face each other and then begin to fight, the shadows keep changing, and when the camera angles show each man's perspective, each man has his shadow to his own right hand side, even though they are opposite each other. (01:14:00)
Continuity mistake: When Menelaus and Paris duel, in some shots there is a thick black chinstrap attached to Menelaus' helmet, which is perfectly visible at his ears, cheeks and under his chin, as the flaps of his helmet move about, yet in the rest of the shots the chinstrap is gone. (It is not a shadow.) (01:14:10)
Continuity mistake: In the middle of the film just after Hector has killed Menelaus, they run away, and on the far away shot, you can see they are some distance from Menelaus body, yet when it cuts to a close-up shot of them running they have barely passed the body. (01:14:25)
Continuity mistake: While Menelaus and Paris duel, Menelaus punches Paris in the face (the first time) and as he spins around spitting blood, the red bruise on Paris' right cheek is perfectly visible, yet in the very next close-up his face is quite pristine - the bruise and blood are actually gone. But of course in the next close-up Paris' cheek bruise is back with blood on his chin as well, and in the following shots the amount of blood goes back and forth. (01:14:35)
Continuity mistake: When Paris and Menelaus duel, the distance between them and each of the two armies changes drastically in different consecutive shots, even when there is minimal movement by the two men. For example, when Menelaus takes Paris' shield away and Paris trips forward in two consecutive shots. (01:14:45)
Continuity mistake: During the duel between Menelaus and Paris, the blade tip on Menelaus' sword actually breaks. It is perfectly visible when he and Paris slam their two swords together, at the start of the same shot just before Menelaus grabs hold of Paris' shield and pushes him away. Of course it's nice and pointy in the following shots. (01:14:50)
Revealing mistake: When Menelaus slices Paris' leg the wound stops bleeding immediately after that shot. (01:15:15)
Continuity mistake: When Hector stabs Menelaus, in the close-up the tip of the blade protrudes at his back a few inches to the right of the second circular design, under the shoulder flap. However, when Hector pulls the blade out, the tip of the blade is directly in the center of the circular decorative design. (01:16:50)
Revealing mistake: Most of the Greek and Trojan armor, in their own respective ways, look more manufactured so they are perfect clones of one another. Real armor from that time would have had lots of imperfections and signs of being individually created and hand-crafted. (01:17:20)
Continuity mistake: Paris drops his sword, and it falls flat on the ground. Then after Menelaus dies, the position of Paris' sword on the ground changes from when he's running to get it, where the blade points more towards the Trojan army (ie. roughly horizontally in his path), to when he finally grabs hold of it, where the sword leans up a bit on its side and the blade points distinctly towards the Greeks (ie. directly away from him). (01:17:35)
Revealing mistake: When Agamemnon and the Greeks charge at the Trojans after Menelaus is killed, in the close-ups during the melee, quite a few of the spears actually wobble in the soldiers' hands, like for example, when the Apollonians throw their spears. (01:18:20)
Revealing mistake: After Menelaus is killed the two armies clash. In the second close-up of the men fighting, when a Trojan slams a large club-like weapon into a Greek's face, the club end bends when blood spurts everywhere. (01:18:20)
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)
Continuity mistake: After Menelaus is killed, when Ajax kills some Trojans and Hector notices him, the pattern of the blood on the front and back of Ajax's shield changes in consecutive shots, such as being clean in an area where it was bloody in a previous shot. (01:19:10)
Continuity mistake: When Ajax fights the Trojans and then Hector, after the death of Menelaus, their positions and the positions of people standing and lying around them, change back and forth in many consecutive shots. During the Hector and Patroclus duel, the Hector and Achilles duel, and the other battles, the positions of duelers, soldiers - as onlookers, fighting or lying on the ground, change drastically between shots throughout the film. (01:19:10)
Continuity mistake: After Menelaus dies, during the Greek charge Hector spots Ajax doing his thing and the rolled white tourniquet around Ajax's leg wounds is clearly visible. When Hector rides toward Ajax, he promptly knocks Hector off his horse and the tourniquet is once again visible, only now it's wider and tied differently, and changes again within the following shots. (01:19:25)
Continuity mistake: While Ajax and Hector fight, Hector head butts Ajax, and three shots later in a wide shot, half of the hammer end of his unusual spear actually breaks and falls to the ground behind him to his left. But lo and behold, in the next close-up the bloody hammer end (bloodier than the previous shot) of his spear is whole and intact. (01:20:00)
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)
Continuity mistake: When Hector grabs the sword from the ground, prior to stabbing Ajax, the blade is covered in blood. But when the blade tip touches Ajax's armor, before it pierces him, the amount of blood on the blade is significantly decreased. (01:20:25)
Continuity mistake: After Ajax's death, when Agamemnon shouts, "Forward!" as they charge, Agamemnon's two horses have very distinctive white markings on their faces. Then when Agamemnon and Odysseus (on the same chariot) retreat, after the cheering of Trojan royalty, in the close-up as Odysseus shouts, "Back to the ships!" the white markings are entirely different, and now both horses are actually wearing blinkers on their bridles to cover their eyes. (01:20:50 - 01:21:55)
Answer: They didn't know the Greeks weren't bringing cavalry. The Greeks did use them and sometimes brought them by sea. It was there to stop a cavalry charge and to break up fighting formations.
LorgSkyegon