Factual error: In the hospital, Corporal Friedrich Schiess tells William and Robert Jones that he's a member of the Natal Mounted Police. In actuality, Cpl. Schiess was a member of the Natal Native Contingent, a distinctly different branch of the colonial forces. The Natal Mounted Police did, however, have three men present at the Battle of Rorke's Drift: Troopers Lugg, Green, and Hunter, and Trooper Henry Lugg later published two detailed accounts of the battle.
Continuity mistake: Chard gets struck on the neck by a Zulu shield, and he falls as if severely wounded. There's no blood on his neck, yet later when Bromhead pulls him upright, his collar is smeared with it. Anyway, how can a blow like that knock him silly? Bromhead was later struck by a Zulu shield on the neck as well, yet he was fine.
Revealing mistake: In the scene where the cavalry arrive (Chard thinks they are coming to help) and ride up to the sandbag wall, you can quite see the lighting being turned on as they get near. For a few seconds they are all in heavy shadow under their hat brims, then suddenly their faces are well lit. It's not a cut, it's one continuous shot.
Continuity mistake: During one of the attacks, the Zulus are charging en masse towards the ramparts manned by British riflemen. When Bromhead yells "Fire!" the soldiers open fire with their rifles....and some Zulus at the REAR of the charge fall dead whilst those in the front continue charging, uninjured.
Factual error: Lieutenants Chard (Stanley Baker) and Bromhead (Michael Caine) and nearly all the soldiers defending Rourke's Drift are clean-shaven. Between 1860 and 1916 all British army personnel, from Field Marshall to Private were not allowed to shave their upper lips. The army rigidly enforced this rule. Thus, all the soldiers defending Rourke's Drift sported moustaches. Many had beards, too.
Factual error: The film seems - through dialogue from the soldiers and the preacher - to suggest that the Zulus were the aggressors ("savages") in this in the actual Anglo Zulu war. In fact the British had crossed illegally into Zululand to provoke a war. The crossing point of the Buffalo river into the Zulu kingdom was Rorke's Drift - and so the Zulu attack on it was not from savage whimsy, but came from a Zulu contingent eager to see action as they were reserves at Isandlwana.
Continuity mistake: During the latter Zulu attacks, a number of charging Zulus fall to the ground clutching their chests as if shot before a single shot has been fired.