Factual error: Throughout the film the British infantry are armed with carbines. These were intended for issue to cavalry and are much shorter than the infantry issue Martini-Henry rifle.
Other mistake: When Melville and Coghill climb out of the river with the colours you can clearly see that the flag is drenched. a few minutes later when they are trying to hold the Zulus at bay you can see the flag fluttering in the wind. It's impossible that the material could dry that quickly when it's that wet.
Other mistake: The scene where the British army is crossing the Buffalo River is in the historic place but they are crossing in the wrong direction.
Continuity mistake: Colour Sergeant Williams and Private Storey are miscredited as "Company Sergeant Major Williams" and "Corporal Storey." Neither is promoted over the course of the film, and both are not only addressed as "Colour Sergeant" and "Private," respectively, but also bear the rank insignia of a Colour Sergeant and a Private, respectively.
Factual error: Simon Ward's character, William Vereker dies after crossing the Buffalo river back into Natal. The real William Vereker died in the camp at Isandlwana: unable to find his own horse, he grabbed a stray to make his escape, but when a native told Vereker the horse was his, Vereker gave the man the horse and was killed by the Zulus moments later.
Factual error: Quartermaster Bloomfield was actually a commissioned officer, not a Sergeant-Major, which is a non-commissioned rank.
Factual error: The commanding officer of the Sikhali Horse was Lt. Charles Raw, not Lt. William Vereker. In the film, while Lt. Raw is featured, he's wearing an incorrect Natal Carbineers uniform.
Factual error: In the credits, it lists Hamilton-Browne of the Natal Native Contingent as a Colonel. He was, in reality, a Lieutenant and a battalion commander. His name is also misspelled as "Hamilton-Brown", as opposed to the proper "Hamilton-Browne".
Factual error: Although the film Zulu Dawn had numerous problems with character age, rank, and affiliation, it is my opinion that the worst of these was the character of "Boy" Pullen. In the film, he's portrayed as a young bugle boy who is apprenticed to Quartermaster Bloomfield (in reality, the attached QM of the 2nd/24th). However, in reality, Pullen was the commissioned Quartermaster of the 1st/24th, and he was very close in age to Bloomfield (whose age is correctly portrayed in the film).
Revealing mistake: The bayonet used by Private Williams after the death of his Sergeant Major is flexible and made of rubber.