Original work print of the movie was 135 minutes long. When it was test-screened to an audience, they almost started a riot after watching this version. This was the only time that the full uncut version was shown, and it caused the studio to decide that it was unreleasable unless massive cuts were made to the film's violent scenes. Some of these cut and never included in any official version scenes include shots of Indian women's breasts being sliced off and thrown around; children's limbs graphically severed (real amputees were employed for these shots); a little girl's legs cut off by wagon wheels; a soldier gleefully cutting an Indian's arms off before shooting another Cheyenne in the eye; the fate of Spotted Wolf, who is beheaded and his head is hoisted as a trophy by a soldier before he tosses it to another soldier, who then throws it off camera. Spotted Wolf's head attached to the stirrup of a cavalryman was not cut and is shown in the release print, and there are stills showing his mutilated body lying on the ground without the head and four cavalrymen running around with his severed head in their hands, howling and laughing while blood is spurting from the neck stump.
In order to recreate the gory Sand Creek massacre of Cheyenne Indians, director Ralph Nelson sought the services of orphaned amputees. Various prosthetic limbs were affixed to missing body parts of these amputees, and then, in one of the most blood-and-guts sequences in film history, these "limbs" were mercilessly hacked off as the cameras rolled.
One of Donald Pleasence's personal favourites among the films he made.
The film provided the first motion picture account of the Sand Creek massacre, one of the most infamous incidents in the history of the American frontier, in which Colorado Territory militia under Colonel John M. Chivington massacred a defenseless village of Cheyenne and Arapaho on the Colorado Eastern Plains.
According to actress Candice Bergen, a large van full of prosthetics was brought in during the filming of the violent battle sequences, full of dummy body parts and animatronics.