You are Dust Jacket #
Counter added 10-18-98
From the Back Cover
    The planet had endured an annihilating cosmic nuclear cataclysm. To all intents and purposes humanoid life had apparently ceased to exist.
    However, there were those who had seen the conflict coming, and who had taken steps accordingly. Man in his natural state would not have been able to survive, but Hengist and MacIlraith, working desperately against time, had produced something different, something that was human in many respects, but which they hoped would be able to survive in an atomic aftermath. Like the phoenix rising from the ashes, the Sons of Tomorrow triumphed over a deadly hostile environment. But the aliens who had started the war returned intent on claiming the planet they thought was dead.
    Could a tiny handful of strangely changed human beings succeed in surviving against such incredible odds? Could they do more than survive? Could they strike back in the name of massacred humanity?
(British, Badger Books SF-100, 1964)