What is the role of the Prussian soldier in the story "The Prisoners"?

To make sure the prisoners are at place

The Prussian soldiers are seen as the antagonists by the French.

They promise not to harm Berthine and her mother in return for food. They keep their promise.

They naively trust Berthine to protect them when she tells them that the French have attacked the house.

Once they are trapped, they shoot at the French soldiers outside through the vent hole.

Faced with drowning, they swallow their pride and surrender to the French militia.

"‘Never mind,’ replied the soldier, who seemed a decent sort of fellow. ‘We won’t do you any harm, but you must give us something to eat. We are nearly dead with hunger and fatigue ...’ The Prussians lay down on the floor, with their feet to the fire and their heads resting on their rolled-up cloaks. Soon all six snored loudly and uninterruptedly in six different keys."

"‘There are the French,’ she stammered; ‘at least two hundred of them. If they find you here they’ll burn the house down. For God’s sake, hurry down into the cellar, and don’t make a ‘sound, whatever you do. If you make any noise we are lost.’ ‘We’ll go, we’ll go,’ replied the terrified officer. ‘Which is the way?’"

"He had accomplished about two-thirds of his journey when a long, crimson flame shot forth from the vent-hole.

The enemy was astir now. They could be heard moving the casks about, talking, splashing through the water. Then, about eight o’clock in the morning, a voice came from the vent-hole ‘I want to speak to the French officer.’ Lavigne replied from the window, taking care not to put his head out too far: ‘Do you surrender?’ ‘I surrender.’"