Second Dawn

Second Dawn is a 1951 science fiction story by Arthur C. Clarke. You can read it online here or here. It begins,

“Here they come,” said Eris, rising to his fore-feet and turning to look down the long valley. For a moment the pain and bitterness had left his thoughts, so the even Jeryl, whose mind was more closely tuned to his than to any other, could scarcely detect it. There was even an undertone of softness that recalled poignantly the Eris she had known in the days before the War—the old Eris who now seemed almost as remote and as lost as if he were lying with all the others out there on the plain.

A dark tide was flowing up the valley, advancing with a curious hesitant motion, making odd pauses and little bounds forward. It was flanked with gold—the thin line of the Atheleni guards, so terrifyingly few compared with the black mass of the prisoners. But they were enough: indeed, they were only needed to guide that aimless river on its faltering way. Yet at the sight of so many thousands of the enemy, Jeryl found herself trembling; instinctively, she moved towards her mate, silver pelt resting against gold. Eris gave no sign that he had understood or even noticed the action.

The fear vanished as Jeryl saw how slowly the dark flood was moving forwards. ...