Title tells all in this ultra low budget sci-fi which boasts flying saucers created by visual effects legend Ray Harryhausen. It aims for a documentary style realism, with voice over narration and lots of pseudo-science, adapted from a non fiction book by Major Donald Keyhoe, formerly of the US marines, who headed up a national committee on UFOs!
But of course it's just entertaining escapism. It's a B film, but it had the advantage in being made for Columbia pictures who had Harryhausen under contract. He creates a good space ship though his models of the collapsing landmarks of Washington DC are no more than ok.
The story mimics the cold war in that it depicts a rapid escalation of military capability, though there is no nuclear. The humanoid invaders (their home planet is left vague) have an effective ultra-sonic weapon and the Americans invent an electro-magnetic ray gun which interferes with their engines. Although at times a six shooter has to do.
Hugh Marlowe is careworn enough to play a research scientist, but perhaps not sufficiently charismatic for an action hero. But he does have an exceptionally sexy assistant/wife in Joan Taylor. This is pioneering sci-fi. Anyone now showing a sky full of UFOs over the monuments of a world famous city owes a debt to Fred Sears and Harryhausen. It's a must-see for fans of fifties sci-fi.