HASTINGS, ENGLAND—Lack of a helmet and not a horse—"My kingdom for a horse!" as Shakespeare has it—cost King Richard III his life, according to a study published Wednesday in the British medical journal The Lancet.

The forensic study of Richard's remains has revealed that the doomed king—the last English monarch to die in combat—suffered 11 wounds at the time of his death at Bosworth Fields in 1485. Nine of these were to his apparently unprotected head, two of them "nonsurvivable," according to Sarah Hainsworth, a forensic scientist at the U.K.'s University of Leicester who was one of the study's authors. (See a 3-D reconstruction of Richard III's face.)

The study, which used whole-body CT scans and micro-CT imaging, paints a grim picture of the king's last moments, when he dismounted in a marsh and was surrounded by at least three and possibly four assailants armed with halberds, swords, and heavy-bladed daggers.

"His injuries represent a sustained attack," says Hainsworth. "The wounds to the skull suggest that he was not wearing a helmet—whether he lost it in the battle or took it off at the end, we don't know. The absence of defensive wounds on his arms and hands suggest that he was still wearing armor over those parts of his body."

Written accounts of the battle all agree that Richard fought bravely, something the forensic evidence bears out. Certainly he took a lot of killing.

View Images The skeleton of Richard III, the last English monarch to die in combat, was discovered last year under a parking lot. Photograph by University of Leicester via Corbis

Researchers noted several "shaving"-type wounds to his skull, where chips of bone sliced off by a weapon of some sort with a serrated edge, as well as a stab wound that penetrated his skull and entered his brain. "It would have hurt, but it didn't kill him," says Hainsworth.

Another deep stabbing blow near the lower right-hand part of his skull penetrated several centimeters into his brain and would ultimately have killed him. But it was an even deeper, more ferocious thrust by a halberd into the lower left side of his skull—delivered perhaps only seconds later and penetrating ten centimeters into his brain—that ended the battle for Richard III.

"This was likely to have been the last blow. Unconsciousness would have been almost instantaneous," says Hainsworth. "Breathing and heartbeat would have stopped sometime afterward. He wouldn't have died immediately. Medieval battlefields were not like that. Forget the movies—there was nothing swift and romantic about death in a medieval battle."

Researchers found evidence of yet another serious, potentially fatal wound to the fallen king's pelvic area, but this they believe was delivered after death—an insult wound.

View Images A blade pierced Richard III's pelvis, penetrating all the way through the bone. Photograph by University of Leices via Corbis

"Had he sustained it in life, it would have caused him to bleed to death, whether in 20 minutes or two hours we can't really say, but it would have killed him," says Hainsworth. "But from the peculiar angle of the thrust, it seems unlikely he sustained it in battle; his armor would have protected him there."

Accounts of the aftermath of the battle describe how his body was draped over the back of a horse and carted away to be buried by monks on the grounds of a nearby church.

"As it lay across the horse's back, it would have been in exactly the right position for someone who wanted to insult the fallen king to give him this one final thrust," says Hainsworth. "And that's what appears to have happened."

Although he was an anointed king of England, the last of the House of York, Richard was given an unceremonious burial and the location of his grave was lost for centuries—until it was discovered by archaeologists in 2012 beneath a parking lot in Leicester.