A Plague of Demons and Other Stories (New ed)

When John Bravais was sent on a secret mission to observe a war in North Africa he found out more than it was safe for him to know - even after he had secretly been surgically transformed so that he was as strong as a Bolo tank, and early as tough: Wolf-like aliens, invisible to the ordinary eye, were harvesting the brains of the fallen fighters!

Brevais might have become the Ultimate Warrior, but still he was only one man against A Plague Of Demons.