Memory (Poul Anderson)

On a far ring planet, known as World Called Maanerek by its inhabitants, only a weak memory of Earth has survived, and technology has declined to preindustrial.

As the story opens, the protagonist Torrek jumps down onto a large bird with a wing spread of nine meters, kills it and lands with it in the sea, to prove himself worthy of marrying Sonna, a girl of the local tribe.

With his memory restored, Torrek begins talking as if no time had passed, sharing all the biased views of his military comrades about the natives.

They bring him to the girl, hoping to obtain information from her that will make it easier to eradicate her people; but Wanen still feels a strong sympathy towards her.

Though his memory of having been Torrek is gone, Wanen's loyalty is now with the inhabitants of the planet, whom he would help to develop technologically and be better prepared for any new incursion by his former compatriots.