Continuity mistake: In a major fight scene two soldiers on opposite sides are jumping and spinning and tapping each other on the head with their swords.
Revealing mistake: After Richard has accepted that he will be king, he appears before a large assembly. Several of the soldiers standing by the walls are obviously plastic dummies. They have unnaturally smooth and blank facial features, and when you can see their hands, they are not grasping their guns, but merely holding their hands stiffly out with the gun between them.
Factual error: When Lt. Lee shoots down the second Messerschmidt in Italy, you can see it is a twin engine plane.
Continuity mistake: When Po is killed by the NVA it is the middle of the night, Captains Cahill and Doyle are close enough to the village to hear the shots and rush back to the village but as they enter the village it is early dawn.