During World War I and II, the Congregation of the Mission, with the approval of the Irish bishops, dedicated the facilities to a range of humanitarian, charitable, and religious causes. The building was again evacuated in 1914 at the start of WWI, and then later housed approximately sixty soldiers wounded at Verdun in 1916.
During World War II, Rector Patrick Travers, a major figure in the college's history, dedicated the building to serving the needs of the country. He maintained a correspondence with the bishops of Ireland, the French and Irish authorities, and the Irish ambassadors in France and Europe to ensure the premises remained neutral. In his letter, dated March 1944, he mentions the permission he gave in 1943 to the Commission de Ravitaillement (Supplies Commission) to store emergency food supplies as "this purpose, besides being a humane one, could not in any way compromise [the] neutrality [of the college]". In total, around three hundred tonnes of food were stored in the college until the German troops retreated from Paris in 1945. He thus participated in passive defense, the aim of which was to protect civilians during war time.