Out of more than 180 science fiction films produced in the United States between 1950 and 1959, twenty were concerned with the notion of an invasion. Of these, a select number used the invasions as metaphors of issues that were of importance to America at the time, such as assaults upon individuality and marriage and debates about the supremacy of the human race. The invasion may be real (The Day the Earth Stood Still and War of the Worlds), dreamed (Invaders from Mars), or the result of a mental breakdown, as seems to be the case in Invasion of the Body Snatchers. Real or not, all of these...