In a biography, regarding the making of Khartoum, it was said not one horse was injured in filming. In later years, it was discovered that over 100 horses were either severely injured resulting in euthanasia or died immediately due to unethical stunt methods.
Charlton Heston actually did bear a strong resemblance to Major General Charles Gordon, but Heston was considerably taller than the real Gordon. Heston stood over 6-foot-2 while the real Gordon was said to have been only about 5-foot-5. Heston was also a few years younger than Gordon was at the time of the events depicted in this film.
The paddle steamer early in the movie where Gordon and Scott leave England is the Princess Elizabeth, built in 1927 and a veteran of the May 1940 evacuation of Dunkirk, where she made four trips carrying British soldiers back to Britain. From 1970 to 1987 she was a pub restaurant in London, near Tower Bridge, then moved to Paris and used as an art gallery. Since 1999 she's been a tourist attraction in Dunkerque, France.
Charlton Heston had hoped that Sir Carol Reed might be persuaded to direct the film, and, when Sir Carol declined, instead pressed for Ken Hughes or Guy Hamilton to be signed for the job. He was not pleased with the way Basil Dearden, who eventually did direct, handled the film.
Bernard Wicki was in the running to direct, and Heston was keen to get either Guy Green (who had done Diamond Head (1962), and helped out on 55 Days at Peking (1963) when everything was falling apart), or Ken Hughes to helm this large scale epic.
This was the final screenplay credit for Robert Ardrey, who had actually done most of the writing for the film several years earlier. By the time the film went into production, Ardrey had already begun to gain a major reputation for his anthropological books, and the year of this film's release coincided with the publication of his most famous book, "The Territorial Imperative". This was a huge international best-seller, and Ardrey was no longer dependent on film work to earn a living wage from writing.
Colonel Stewart says "they've captured 10,000 Remington rifles." The Egyptian Army and Gendarmes were issued with Remington rifles, which were standard issue from 1867 until the mid 1880s. At the time only the British Army was issued with the Martini-Henry rifle.