How does Guy de Maupassant use imagery in Boule de Suif?

Boule de Suif opens with a description of French soldiers retreating from the advancing Prussian army. They are fleeing through Rouen as the Prussians begin to take hold of the city. Many Prussians are boarding up with townspeople and, in general, acting quite respectable in the townspeople's homes. Outside in the streets, they are gruffer and carry themselves with a stronger, more ostentatious air. Many who attempt to flee the city are held captive or turned back.