Why are the roads in France different these days?

As Darnay traveled over the roads of France, he saw that the fields were impoverished, home had been burnt to the ground, and patrols were everywhere.

Happily, however, there was sleep in Beauvais that night to help them out of it and they passed on once more into solitude and loneliness: jingling through the untimely cold and wet, among impoverished fields that had yielded no fruits of the earth that year, diversified by the blackened remains of burnt houses, and by the sudden emergence from ambuscade, and sharp reining up across their way, of patriot patrols on the watch on all the roads.