The film stars Charlton Heston as Gordon, and the great Laurence Olivier, with much dark make-up, as the Mahdi, Muhammad Ahmad. Although the film contains some archaic portrayals that we would now term as 'orientalism', and some of the acting and scenery is ham-handed for our jaded 21st century tastes, it is still of great value.
'Khartoum', the movie, combines great adventure with some hard and true lessons about life. Gordon is suitably played in the classic Heston style, while the Mahdi is almost comically portrayed by Olivier: what kind of inspired leader sticks his small finger into the gap between his front teeth when deep in thought?
They both represent men who have committed their lives fully to their purpose. Both are 'laws unto themselves', moving with certitude to realize their missions: Mahdi to remove the British; Gordon to save Khartoum from annihilation. Both are fiercely independent. When Gordon is asked why, as a committed Christian he would not turn the other cheek to an enemy, he casually says,"because I am not Jesus."
But, there's an added twist, not only are the two protagonists highly self-motivated, they are also essential to each other. They know one is not fulfilled without the other; they are effectively collaborators in a grander scheme. Gordon cannot live himself out as guardian of Khartoum without the Mahdi's predations, and Muhammad Ahmad cannot rise to glory without the presence of Gordon Pasha in Khartoum.
In a climactic scene, they meet to negotiate terms only to find that each is ready to die for his cause. And so, in turn, they do, always retaining the greatest respect for each other, opposites fulfilling a hidden purpose.
After Khartoum is taken by the Mahdi's army, and Gordon is killed, his head is brought to the Sudanese leader stuck upon a long spear. Mahdi/Olivier gazes at it in horror, and screams with anger at his henchmen for having so defiled a great man, his enemy, Gordon of Khartoum.