Operation Terror

Sometimes called the "Dean of SF," Murray Leinster (the pen name of William Fitzgerald Jenkins) won both a Hugo Award and a Sideways Award for Alternate History for his science fiction tales. First published in 1962, "Operation Terror" is a novel of alien invasion -- about non-human beings landing on Earth with the intent of conquest. It's the story of how we respond to the threat. The hero of the story is Lockley, who suspects that human traitors may be involved in the alien attack and develops a portable device that deflects the alien terror beams with amazing and unforeseen circumstances.