The 1900s begins with a series of important visits to Montecassino: the German Emperor William II, the musician D. Lorenzo Perosi and Giovanni Battista Montini, the future Pope Paul VI, visiting for a spiritual exercise course for the FUCI students.

On May 6, 1913, together with the Beuron Abbot and the future Archbishop Ildefonso Schuster of Milan, Abbot Diamare consecrates the Crypt with its altars. The new Abbot was known for his laic boarding school management and for his great pastoral works.
In 1929, several cultural initiatives followed in conjunction with the 14th centennial anniversary of the founding of Montecassino. The Monastery was confirmed as the center of spiritual life and of rigorous studies. A historic art exhibit was also inaugurated and was open until the end of 1943 antedating that museum which was then realized in 1980 during the 15th centennial of the birth of Saint Benedict.
Some Roman headstones, undamaged during the bombardments, were placed along the staircase to the ancient doorway in 1929. The staircase was later adorned with other pieces found after the war. During this year, the cable-car appeared which connected the Monastery to the city. It was later inaugurated in 1930. Also during 1929 a drinkable water system was realized which replaced the rainwater tanks of the Monastery.
All of these works framed the active life that evolved in the Monastery, where a numerous community and about 110 boarding school students were present.
This hard-working life seemed to foresee a new stability and activity in the Abbey after the uncertainties during the second half of the 1800s, but tragic events were on the horizon: on September 1, 1939, Germany invaded Poland beginning World War II.
In 1943 the war reached the territory of Cassino bringing devastation and death not only in the city but also in the Monastery, which was destroyed by a terrible bombardment on February 15, 1944.