Eric Frank Russell's "The Glass Eye" (short story, alien invasion)

It has been quite some time since I saw a really good story of Russell; this one breaks the jinx. It's as good as anything by Russell at this story length.

Story summary.

Two arrogant "Sagittarian" invaders, Qvord & Eenif, have finally discovered Earth, & want it. So they plan to soften up the inhabitants for slavery, before masters arrive in hordes.

Near the end of the week long softening, they'll finally face the horror...

Notes.

1. Title refers to a camera lens, employed as a weapon by humans.

Fact sheet.

First published: Astounding, March 1949.
Rating: A.
Among the stories edited by John Campbell for Astounding/Analog. 
Related: Stories of Eric Frank Russell (annotated list).