The troops, wishing to be rid of impedimenta, were sending them forward by railway and highway.

That must be it.

So all through the night, he interpreted the incessant bustle as the passing of vehicles filled with the wounded, with munitions and eatables, like those which had filed by in the afternoon.
Toward morning he fell asleep through sheer weariness, and when he awoke late in the day his first glance was toward the road.

He saw it filled with men and horses dragging some rolling objects.

But these men were carrying guns and were formed in battalions and regiments.