This movie's low budget gives it a rough, desperate, impoverished, almost documentary kind of feel, strangely anticipating the faux documentaries of the 21st Century and the gimmicks of 'Blair Witch Project' and 'Cloverfield'. This works to its advantage, along with a script and actors that somehow give an aire of verisimilitude to the somewhat far-fetched plot.
There is perhaps an allegorical appeal to the scenario...diverse characters, thrown together by fate as society disintegrates, alternately waiting for the end and hoping for a miracle. The various characters form an imperfect microcosm for society, and it seems strangely plausible that a gangster and his moll would occupy the End Time with cheap thrills and attempts to seize power, while a dedicated father and military officer would cling desperately to authority and structure.
There is a really great, understatedly bizarre scene that stands out: in this scene, Our Hero Richard Denning is talking with his brother, who, due to excessive exposure to atomic radiation, is slowly transforming into a cannibalistic monster. While Denning and the rest are confined to a small, radiation free valley, the brother, because he is mutating, goes in and out of the radiation zone at will. He tells Denning this: 'There's new things going on out there...exciting things!' One can only imagine what kind of new things in a post-apocalyptic world a cannibalistic atomic mutant would find 'exciting.' It's a moment of cinematic genius, that's for sure.
The retired military officer who commands the survivors thumps the Bible a few times, and there are a number of overt Judeo-Christian references. The ending certainly contains a religious aspect. It would be interesting to know if Roger Corman had obtained funding from a religious group to make this film, or if the references were included simply for artistic reasons.
Either way, this is the earliest example I have seen wherein the nuclear doomsday scenario is wedded to the Christian concept of end times. From the 1960's onward until now, believers in the Christian Rapture have had a field day borrowing nuclear End Times material for their tracts, sermons, and novels...this film might be seminal in that regard. Still, I won't fault Roger Corman for the gawdawful 'Left Behind' novels and movies. No one would produce that junk if there weren't fools who would buy it.