Rural populations remained strangers to Christianity despite scattered islands in Arlon, Bitburg, Altrier and Dalheim.

In the late 5th century, the Church was cut off from the power held by the new, Frankish arrivals, who were dedicated to the cult of Odin.

Under the Carolingians, the Frankish church's reorganisation went underway, and the evangelisation of the area of Luxembourg was facilitated by the official recognition of Christianity.

[1] The work of these missionaries was complemented by the foundation of monasteries in the 7th and 8th centuries: St. Maximin's Abbey in Trier (633), Stavelot-Malmedy (650), Andagium (687).

Irmine, the abbess of Oeren near Trier, granted him land in Echternach, and possessions in Badelingen, Batzen, Osweiler, and a vineyard in Vianden.

The French Revolutionaries' pillages, and the flight of the monks towards Germany, taking with them their treasures which they later sold, caused the abbey's works of medieval religious art to be dispersed up to the present day throughout the libraries of Nuremberg, Bremen, Trier, Darmstadt, Hamburg, El Escorial and Paris.

[3] They promoted the veneration of the Virgin Mary, as "Our Lady of Luxembourg" and “Comforter of the Afflicted” (Consolix Afflictorum), in times of plague and war.

[3] This devotion continues to this day in the form of a national pilgrimage, the Octave, celebrated every year for two weeks in the period after Easter.

The Council often made use of this to retain control of the Catholic Reformation, and to force foreign bishops to recognise its authority.

As to the clergy, contemporary sources mention specifically the sires prélats, as it was only the large abbeys that were represented, as large-scale landowners.

[7] As in the rest of the Habsburg Netherlands, the situation of the Catholic Church in Luxembourg was precarious: the number of clerics who drank or had relationships was high, and the parishioners were often left to themselves, without regular religious instruction, and turned to superstition.

No order or pastoral letter, whether from the pope or the bishop, could be published in the duchy without the consent of the Conseil de Luxembourg.

This function, defined in 1586 by Philip II, was particularly present in the duchy of Luxembourg, which was handicapped by large distances and the poor urban network.

After the reforms of Joseph II, the contemplative orders were suppressed, while the large monasteries disappeared in the French Revolution.

After the 1815 Congress of Vienna, which raised Luxembourg to the rank of Grand Duchy in personal union with the crown of the Netherlands, Pope Pius VII attached in 1823 the territory to the Diocese of Namur.

On the one hand, the bishop, Joseph Laurent Philippe, was bedridden due to illness, and was therefore in no state to provide active opposition.

On the other hand, the Bishop did not want to further antagonise the occupiers and endanger the already fragile religious life of the Church, which was heavily restricted during wartime.

Bishop Philippe did, however, refuse to meet with the Nazi leadership, and made preparations in case his post should fall vacant.

[13][14] At the same time, the diocese administration remained one of very few Luxembourgish institutions that stayed intact during the war, although this was in doubt for a while, and the occupation authorities did consider deporting the Bishop.