The Abbey of Montecassino lived through moments of great uncertainty in the beginning of the 1800s until the return of the Bourbon reign. The mountain was occupied by brigands and the monks were forced to supply daily board to the soldiers. The actions in 1820 brought consequences even to the Abbey of Montecassino which was occupied by the Austrian troops in March, 1821, and the monks were forced to give up their rooms. While in Italy the revolutionary actions spread, Montecassino saw a renewed cultural zeal with Luigi Tosti who epitomized in himself the faith of the traditions of the Church and a true italianism.

With Frederick I there was also a period of political repressiveness for Montecassino: the Bourbon police searched the Cassino archives and seized the Monastery's printery. During that year, the laic boarding school of Montecassino was founded.

Although Montecassino was assured that it would have been saved from the application of the abolition laws of 1866, in 1868 the law was also applied to Montecassino. This lead to the expropriation of all the possessions belonging to the monastic community with all its patrimonial properties. The Monastery was declared a National Monument: the Abbot could continue to have the role of Ordinary for the Cassino Diocese. The Abbatial Church constituted the residence of the capital and the monks could remain in the Abbey as cathedral church canons and custodians of the abbatial building.

In 1875, Montecassino was enriched with the meteorologic Observatory which began operating only in 1876. On the anniversary of the birth of Saint Benedict in the 14th century, the Tower, the core of the original Monastery inhabited by Saint Benedict, was consecrated. It was renovated and ornamented by Desiderius Lenz's Beuron art school.