The battles of Castelfidardo takes place the September 18th 1860, with Castelfidardo, small town of the area of the Marches. The Piedmontese troops carrying out the war of Italian unification demolish the pontifical troops there.

Following this battle, the Papal States are reduced to the surface of current the Latium.

The battle remained in the memories bloody, and to be delivered under condition of most unequal (less than 10.000 Pontifical against nearly 60.000 Piedmontese). The pontifical army counted in its rows of the volunteers of various countries of Europe, among which the French nationals and Belgian constituted a Franco-Belgian battalion. Among the French volunteers appeared many noble of the West of France: by consulting, after the battle, the list of dead and the pontifical casualties the Piedmontese general Cialdini said, with a humor of blackest, " One would say a list of guests to a ball of Louis XIV! … ".

The Franco-Belgian battalion gave rise to the body of the pontifical Zouaves.