The old man is just one of many thousands of refugees caught up in the middle of the Spanish Civil War. Having already been forced to up sticks from his hometown, the old man has to move on once more to escape the imminent arrival of Fascist troops. Yet the old man's too tired, too world-weary to comply with the soldier's advice to leave immediately.
The soldier asks the old man some questions about his background. Although we never discover what, if anything, his profession was back in San Carlos, we do find out that he used to take care of some animals. In fact, the old man can think of nothing else but the welfare of the animals he was forced to leave behind. We get the impression that the animals were his whole life; and that now he's no longer able to take care of them, that life effectively has no further purpose. So the old man remains seated by the side of the dusty road, unwilling to go on any further, seemingly indifferent to his fate.