Why has the fishing experience been special for the two friends in "Two Friends" by Guy de Maupassant?

The two friends, Monsieur Sauvage and Monsieur Morissot, have visited their favorite fishing spot on the river many times over the years and have always enjoyed the tranquility and the innocent adventure. But their latest experience proves to be quite different from the past. They know they shouldn't be going at all. The countryside has been evacuated. They are motivated by two factors. One is that with Paris under siege, the people are starving. 

Paris was blockaded, starved, in its death agony. Sparrows were becoming scarcer and scarcer on the rooftops and the sewers were being depopulated. One ate whatever one could get.

The two friends are hungry. This accounts for the second factor. They drink two absinthes apiece at cafes and become intoxicated. This hasn't happened in the past, but on this day:

On leaving they felt giddy, muddled, as one does after drinking on an empty stomach. It was mild. A caressing breeze touched their faces.

The absinthe affects them more than usual because they haven't eaten for days. His intoxication emboldens Monsieur Sauvage to suggest that they go fishing at their usual place, and Monsieur Morissot's intoxication emboldens him to agree to the adventure. Since they are older men and civilians, they do not expect to be harmed even if they should run into the dreaded Prussians.

The countryside is beautiful and peaceful. Just like in the old days, excepted that it is depopulated. They catch a lot of fish because no one has fished there in a long while due to the war. This was in the days before trench warfare and armored tanks. The Franco-Prussian War began in September of 1870 and ended in January of 1871. The French suffered a humiliating defeat and were forced to pay exorbitant indemnity as well as losing the provinces of Alsace and Lorraine to Germany. The two friends see no signs of Prussian soldiers and assume the Prussian forces are some distance away.

Pointing up to the heights, M. Sauvage murmured, "The Prussians are up there!" And a feeling of uneasiness paralyzed the two friends as they faced this deserted region.

But to their dismay they run into a small detachment of Prussian soldiers and are taken prisoner. 

But they shuddered in terror when they realized that someone had just come up behind them, and looking around they saw four men standing almost at their elbows, four tall men, armed and bearded, dressed like liveried servants, with flat caps on their heads, pointing rifles at them.

The Prussian officer promises to let them go free if they will tell him the password they had been given to enable them to return through the French lines. These two innocent, harmless men show unexpected courage when both refuse to divulge the password. The Prussian officer orders them shot and thrown into the river. He enjoys their catch of fish himself.

Maupassant hated the Germans after the French defeat. He wrote a number of stories which were intended to fan the hatred felt by the entire French nation. Maupassant's often-anthologized story "Boule de Suif" is another example of his anti-German theme. He typically makes the Prussian invaders seem inhuman and sadistic. The reader feels cold chills when the two very likable and very civilized fishering-friends fall into the clutches of the fiendish, barbaric enemy.