Earthmen Die Hard!

A particularly virulent germ-life infested the third planet of Sol. It was obvious the world had to be decontaminated. But the aliens found—
They climbed the hill together, arm in arm. At the crest, they stopped and looked back into the moon-brightened valley where the thin needle of metal pointed skyward.
The night wind blew her dress tightly about her slim legs, and she reached a hand to her head to keep the blonde curls from whipping about her face.
He put his arm about her waist, squeezed her gently. Only a few more hours to wait, he said, reassuringly.
The great ship from beyond the Galaxy drew alongside the tiny planet, matched its orbit, cut its drive, and drifted slightly toward the lone moon. The ship was nearly as large as the planet itself, but there was no interchange of gravity between the two bodies, for the ship was of a substance made beyond the stars.
Inspector Ryt looked at his sky chart. Yes, it was Sol III. Then he looked through the port hole at his left and adjusted the lens. Then he swore by the Seven Sister Suns of Sagittarius.
The lens showed him the moonlit side of the planet. There were lights there, little rows of lights forming checkered patterns in various areas. And there were other lights, greater lights which flickered viciously among the patterns, leaving squat, circular clouds above them.
Ryt's cheeks puffed out in uncontrollable wrath. Contaminated! he bellowed. And they are warring on each other!
He turned from the lens, his gross body glowing in red anger. Krembyl! he screamed. Krembyl!
The door at the far side of the room swung open, and the entity called Krembyl fluttered in. Yes? he asked, his body trembling at the manner in which his name had rung out.
Your records show Sol III as sterile. Decontaminated!
Y-yes, sir, Krembyl stammered. I—I took care of it myself. Just a—a few days ago....