During the first centuries of the Middle Ages, French influence in Flanders was particularly noticeable in the monasteries. Almost in every monastery Walloon and Flemish monks lived side by side, and it became necessary that their abbots should be able to make themselves understood by both sections of the community. Thierry of St. Trond was chosen by the monks of St. Peter at Ghent "quoniam Theutonica et Gaulonica lingua expeditus." Examples abound of bishops, teachers and preachers able to express themselves in Flemish and French. The "Cantilene of Ste. Eulalie," the oldest poem written in the French language, was discovered in the monastery of St. Amand together with one of the oldest German writings, the "Ludwigslied." The Clunisian influence tended also to spread the use of French in the northern districts. [_BI-LINGUALISM_] The same bilingual characteristic may be found among the nobles, who met frequently in the course of their military expeditions or peaceful tournaments. Intermarriages between families belonging to both parts of Lotharingia and Flanders were frequent. Besides, most of the large domains lay across the language frontier. The knowledge of French soon became an essential condition of a good education, and the children of Flemish lords were sent to French abbeys in order to perfect their knowledge of the language. It may be assumed that, at the end of the eleventh century, the majority of the aristocracy was bilingual. It was one of the reasons which gave the Belgian nobles such a prominent position in the crusades. A contemporary writer, Otto of Friesingen, explains that Godfrey of Bouillon was placed at the head of the crusaders because, "brought up on the frontier between romanized and Teutonic people, he knew both languages equally well." This penetration of French, not only in Flanders, which was nominally attached to the kingdom of France, but also in Lotharingia and even in Liege, the centre of German influence, is all the more remarkable as it implied no political hegemony, the counts of Flanders being practically independent, at the time, and the other nobles attached to the Empire. It was not introduced by conquest, as in England in the eleventh century, or through immigration, like German into Bohemia or into the Baltic States. The race of the northern provinces remained relatively pure, and the adoption of a second language by the aristocracy can only be explained by the intimate relations created between Thiois (Flemings) and Walloons owing to political conditions, to diocesan boundaries and social intercourse.