Visible crew/equipment: In the scene where Jeremy Kemp and George Peppard are playing daredevil in their planes and Kemp's plane hits a brick tower there is a shot of the plane plummeting to the ground. The alert viewer can see the shiny metal wires that were used to support and guide the plane on its way to the ground.
Continuity mistake: The shadows in the scene with Lawrence sleeping on his camel are short because it's the middle of the day. In the next shot you see long shadows on the sand. When Ali wakes up Lawrence they are short again. (01:01:41)
Visible crew/equipment: In the scene near the beginning of the film, when the 2 brothers are fixing to leave to join the army. After the mother gives them the flag, the shot changes to the 2 brothers. You can see the boom mic and the camera in the reflection of their shiny brass buckles.
Continuity mistake: When Leonidas, and presumably all the other Spartans, use their spears to clear their shields of arrows after the arrow shower from Persian archers, the tips of the arrows are still visibly left on all their shields. In the next shot, when the Spartans regroup for the Persian cavalry charge, the arrow tips are gone. (Granted, this is a highly stylized movie based on a comic book, but that does not change the fact that this is a continuity error.)
Factual error: I normally wouldn't bother with this sort of nitpicking, but this film specifically claims to be historically researched - and it's full of historical blunders. For a start, the film is set as the Empire withdraws its last troops from Britain - which was in 407 AD. Now Artorius Castus was a real Roman officer who really did command Sarmatian foederati at Hadrian's Wall, but he died around 200 AD. Cerdic was a real Saxon warlord who did go raiding the Britons with his son Cynric, but he did this in the early 500s. Pelagius really was tried for heresy, but he was acquitted and died of old age; the trial was a decade after this setting, and in the fifth century you couldn't be executed for heresy anyway. Also in the fifth century the Pope had no authority over Imperial troops. I could go on and on but that will do for now.
Revealing mistake: When the boat is supposedly surrounded by a swarm of flies, they're really just relatively few flies trapped between two panes of glass in front of the camera lens. Evidence: whenever the camera moves, the "swarm" moves with it against the background, and you can even see some of the insects walking on the surface of the glass.
Continuity mistake: When the German NCO begins to walk up the sand dune he has a stick grenade in his right boot. Next shot half way up the dune, the grenade has changed boots.
Visible crew/equipment: At the surrender of the fort, as the English are marching out, the French general removers his hat. The English Commander, Monroe, says "The fort is yours, Monsieur". Look over his shoulder. In the distant valley you can see what are either two tourist busses or perhaps mobile catering vans. (01:05:40)
Continuity mistake: In the first scene of their "training" for the big mission, the text "Somewhere near Galveston, TX" shows up as a subtitle on the screen. As it does this, there is a nice, dark aerial shot of mountainous terrain which is supposedly to hide the troops from any outsiders. The problem is, there are no mountains within hundreds of miles of the Island of Galveston. The whole terrain in this area is so flat that you can practically see from one side of the island to the other. (00:21:45)
Factual error: The rifles the British soldiers carried in the film were Lee Enfield rifle No. 4's, these did not go into production until WW2. They should have been using an earlier version of the Lee Enfield rifle.
Revealing mistake: After Lansbury makes her clothes start to move, her nightgown attacks someone and you can notice the strings that make the gown move.
Revealing mistake: In the beginning, there is a scene where Sen. Shaw is watching Raymond make a speech on a TV screen. It was obviously put in in post-production because the aide immediately next to the screen is nodding and clapping in agreement at inappropiate times.
Revealing mistake: In one scene just before the attack on a big Hunter the young captain (Jürgen Prochnow) is sitting with his charts. Beside him he has got a glass of beer standing. The sub lurches heavily right and left in the hard weather, but the surface of the liquid stays the same.