The alien invasion is a common theme in science fiction stories and film, in which extraterrestrials invade Earth either to exterminate and supplant human life, enslave it under a colonial system, harvest humans for food, steal the planet's resources, or destroy the planet altogether.
The invasion scenario has been used as an allegory for a protest against military hegemony and the societal ills of the time. H.G. Wells' novel The War of the Worlds exploits invasion panics that were common when science fiction was first emerging as a genre.
Prospects of invasion tended to vary with the state of current affairs, and current perceptions of threat. Alien invasion was a common metaphor in United States science fiction during the Cold War, illustrating the fears of foreign (e.g. Soviet Union) occupation and nuclear devastation of the American people. Examples of these stories include The Liberation of Earth by William Tenn and The Body Snatchers.
In the invasion trope, fictional aliens contacting Earth tend to either observe (sometimes using experiments) or invade, rather than help the population of Earth acquire the capacity to participate in interplanetary affairs. There have been a few exceptions, such as the alien-initiated first contact that begins the 1951 film The Day the Earth Stood Still, and the Vulcan-initiated first contact that concludes the 1996 film Star Trek: First Contact (although after a failed invasion by the Borg in the rest of the film). In both cases, aliens decide to visit Earth only after noticing that its inhabitants have reached a threshold level of technology: nuclear weapons combined with space travel in the first case, and faster-than-light travel using warp drive technology in the second.
Technically, a human invasion of an alien species is also an alien invasion, as from the viewpoint of the aliens, humans are the aliens. Such stories are much rarer than aliens attacking humans stories. Examples include the 1989 video game Phantasy Star II, the 2007 film Battle for Terra, The Martian Chronicles by Ray Bradbury, the Imperium of Man in the Warhammer 40,000 universe, the 2009 movies Planet 51 and the 2011 movie Mars Needs Moms.
As well as being a sub-genre of science fiction, these kinds of books can be considered a sub-genre of Invasion literature, which also includes fictional depictions of humans invaded by other humans (for example, a fictional invasion of England by a hostile France strongly influenced Wells' depiction of a Martian invasion).
Read more about Alien Invasion: Origins, Variations, Notable Examples, Planetary Defense in Science Fiction
Famous quotes containing the words alien and/or invasion:
“The Jew is neither a newcomer nor an alien in this country or on this continent; his Americanism is as original and ancient as that of any race or people with the exception of the American Indian and other aborigines. He came in the caravels of Columbus, and he knocked at the gates of New Amsterdam only thirty-five years after the Pilgrim Fathers stepped ashore on Plymouth Rock.”
—Oscar Solomon Straus (1850–1926)
“In our governments the real power lies in the majority of the community, and the invasion of private rights is chiefly to be apprehended, not from the acts of government contrary to the sense of the constituents, but from the acts in which government is the mere instrument of the majority.”
—James Madison (1751–1836)