After receiving doctorates in theology and philosophy, he headed the Augustinian College Saint Monica in Rome, where he hid many refugees including military officers, Jews and anti-fascist politicians during the war years.

[1] [citation needed] On 13 January 1951, Pope Pius XII named him Titular Bishop of Porphyreon, prefect of the Papal Sacristy, and Vicar General of Vatican City.

[3] Throughout his life, Van Lierde was an ardent admirer of Pope Pius XII, whose determination and courage to save lives during the German occupation of Rome he repeatedly described.

[5] From 1958 to 1995, Van Lierde presided over the annual liturgical celebrations for Pope Pius XII in the crypt of Saint Peter Basilica.

In presence of Cardinal Joseph Ratzinger, he led the funeral services of Madre Pascalina Lehnert in the Vatican's Campo Santo Teutonico.