“The Liberation of Earth,” William Tenn (Philip Klass) 1953 – Warring alien cultures arrive on Earth to “liberate” it—and establish military bases. Humanity is nearly destroyed, and the aliens abandon Earth, as it’s too primitive to be worth occupying.
Comments: Read in The Penguin Science Fiction Omnibus. Wikipedia: “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.”
Author: Wikipedia: “William Tenn was the pseudonym of Philip Klass (May 9, 1920 – February 7, 2010), a British-born American science fiction author, notable for many stories with satirical elements.” See Matthew Cheney’s review of Tenn’s fiction.