Read it through once

On an incline over which a road wound he saw wild and desperate rushes of men perpetually backward and forward in riotous surges. These parts of the opposing armies were two long waves that pitched upon each other madly at dictated points. To and fro they swelled. Sometimes, one side by its yells and cheers would proclaim decisive blows, but a moment later the other side would be all yells and cheers. Once the youth saw a spray of light forms go in houndlike leaps toward the waving blue lines. There was much howling, and presently it went away with a vast mouthful of prisoners. Again, he saw a blue wave dash with such thunderous force against a gray obstruction that it seemed to clear the earth of it and leave nothing but trampled sod. And always in their swift and deadly rushes to and fro the men screamed and yelled like maniacs.