From Invasion to Cooperation: The Shifting Portrayal of Aliens in Postwar Science Fiction

To the point

Since 1940, alien-focused science fiction has swung between invasion narratives and visions of cooperative futures that push human evolution, reflecting wartime and Cold War anxieties and shaped by writers such as John W. Campbell, Arthur C. Clarke, Stanislaw Lem, Ray Bradbury, and Carl Sagan.

science fiction involving extraterrestrials, after 1940
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science fiction involving extraterrestrials, after 1940

Alien invasion and subversion became popular themes in American and British (though not Russian) science fiction during the Second World War and the Cold War years that followed.