The Liberation of Earth

"The Liberation of Earth" is a science fiction short story by William Tenn, written in 1950, first published in 1953, and reprinted over a dozen times in various anthologies and in 1955 in the William Tenn collection Of all Possible Worlds. The story, which Tenn described as having been inspired by the Korean War, portrays Earth as the battleground between two powerful alien races, the Troxxt and the Dendi, who repeatedly "liberate" it from each other.
-From Wikipedia