The fake-alien-invasion plot idea dates to an 1923 French tale

Evidence

Deyo suggests that an appropriate catalyst would be an invasion by UFOs, in either of two scenarios. One envisions a fake extraterrestrial invasion, in which conspirators on earth produce an armada of seemingly alien fl ying saucers manned by human impostors, in order to create an artifi - cial common enemy against which humanity could unite under a world government—an idea similar to that proposed by André Maurois in his 1923 tale, The Next Chapter: The War against the Moon. — Michael Barkun, A Culture of Conspiracy, 318

Categorization

• CANDY: A perfect trivia hook: the ‘fake alien invasion to unite humanity’ plot, now a sci-fi cliché, traces to Maurois in 1923.
• FICTION: The nested fake-alien-invasion conceit is a rich premise fuel for speculative-fiction worldbuilding.