Burt Lancaster, who pulls off an Irish burr, was reportedly "tone deaf" when it came to accents. Lancaster also was challenged by having to learn how to do things like ride a horse with only one arm.
The real-life Lord Chelmsford was able to save his job by fudging a lot of facts, including inflating the size of the Zulu army from 20,000 to 60,000 and scapegoating Colonel Dunsford. Because of the less significant British victory at Rorke's Drift the same day, Chelmsford later received a promotion due to the influence of his chief supporter, Queen Victoria.
The film claims that the British were defeated because of lack of ammunition due to boxes being "screwed down." According to historical records and archaeological evidence, the ammunition boxes were designed to be opened quickly by knocking off the center section of the lid. In one scene near the end of the battle, someone uses a rifle butt to knock out the center panel. The firing lines were spread too far out, reducing the effectiveness of the British volley fire. The rifles started to jam and misfire after prolonged firing, enabling the Zulus, who had suffered terrible losses, to close with the firing lines and overwhelm the British in mass charges.
Peter O'Toole was in such poor health that much of the crew believed this would be his final film. Ironically, O'Toole ended up outliving the rest of the film's front-billed cast.
Ronald Lacey replaced John Hurt after South African authorities confused Hurt with American actor John Heard, who had been arrested in an anti-Apartheid march, and refused to issue a visa.