At the age of 16 he finally obtained his father's permission to enlist in the Papal Zouaves, serving until experiencing a vocation to monastic life.

[1] On 3 February 1869 Félix entered Beuron Archabbey in Germany, made his religious profession on 15 August 1870, and received the name "Hildebrand."

He had been drawn to this newly founded monastery led by Archabbot Maurus Wolter with the hope of one day restoring a monastic presence in his home country of Belgium.

He received his abbatial blessing at the Abbey of Monte Cassino on 5 October 1890 with the officiating prelate being Cardinal San Felice, O.S.B.

His plans were accepted and the laying of the cornerstone on the Aventine Hill in Rome on 19 April 1893 would also see the gathering of abbots from around the world.

In 1912, after a stroke, he offered his resignation on health grounds but was kept in his position by Pope Pius X, with a coadjutor appointed to lighten his work.