Swordsman of Lost Terra by Poul Anderson — Read

Now the armies of Ganasth moved against Ryvan city itself. From all the plundered empire they streamed in, to ring the town in a living wall and hem the defenders within a fence of spears. And when the whole host was gathered, which took about ten sleeps from the time the Killorners arrived, they stormed the city.

Up the long slope of the hills on which Ryvan stood they came, running, bounding, holding up shields against the steady hail of missiles from the walls. Forward, silent and blank-faced, no noise in them save the crashing of thousands of feet and the high demon-music of their warmaking -- dying, strewing the ground with their corpses, but leaping over the fallen and raging against the walls.