Continuity mistake: Aboard the ship going back to Troy, when Paris walks over to Hector he places his hands on the rail of the ship, and the collar on Paris' left side hangs off his shoulder, yet in the next close-up it's properly on by his neck. (00:14:45)
Continuity mistake: In the morning, while Achilles watches Briseis sleep, her arm extends way over the edge of the bed in the wide shots facing her, yet in the shots facing the doorway her position differs and even her hand doesn't reach the edge of the bed. (01:33:05)
Continuity mistake: When Hector tries to stop Helen from running away at night, her hair keeps changing; one can see in her "back" shots, sometimes her hair is completely down, and other times her hair has two twists in it. It keeps changing throughout the scene. Also, in the same scene, the front of her hair is sometimes a little frizzy and curly, and sometimes it is smooth and straight. (01:01:45)
Continuity mistake: The scars and scratches on Boagrius' face and body change significantly and some scratches disappear, between his first few close-ups and then when Achilles moves toward him. For instance, the scars on his chest are less severe in the close-ups when Achilles heads toward him. (00:06:45 - 00:07:45)
Continuity mistake: When Helen sutures Paris' leg wound, as he lies on the bed, the collar on his shirt fits round his neck properly, yet in the next close-up it hangs down off his shoulder, though he does not move. (01:24:35)
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