His mission nearly came to a tragic end before it had properly begun. On his way to Brussels, he went by way of Mechlin to visit Cardinal Sterckx, the archbishop. While crossing a canal bridge near Vilvorde the horses took fright and were about to plunge into the water when a priest of the neighborhood courageously seized them by the reins. Pecci refused to ride any further, but left the coach and walked all the way to the capital, where the king joked pleasantly with him about his accident and his coming into Brussels on foot.
The division among the religious and political parties of Belgium with their perpetual intrigues, rendered the post of nuncio to Belgium extremely delicate and difficult...Parties of all sorts, some anti-Catholic, came into being. The country became a hotbed of secret societies conspiring against the monarchical institutions of Europe.
The task was almost insurmountably difficult for any nuncio coming to Brussels, as can be gathered from a long letter Lambruschini wrote as a private instruction for Pecci in which he refers to the complete separation of Church and State. The Pope had already condemned the novelties and systems of Lamennais. Archbishop Pecci was to see that teachers were no longer under the influence of this man, whose errors had caused the bishops of Belgium to create the University of Louvain. At the time of the new nuncio's appointment, the bishops had a bill before the government asking for recognition of the university as a legally incorporated body. Pecci was instructed to see that the bill was withdrawn as the time was not propitious for it. There were constant conflicts between various parties, Church and state, prelates and laity. The parties were struggling for power, and this caused heated opinions and policies, even in other countries of Europe...
How the nuncio felt the weight of his responsibility in these circumstances is described in a letter he wrote to his brother Charles: "You will pardon me, dear brother, for devoting myself entirely to Belgium where the Lord's will has called me to fill an exalted office. Its duties and concerns are extremely delicate and difficult, as you may easily understand without my mentioning them. I ask you always to remember me in your prayers, so that the Lord may assist me with His holy grace. May the appeal of your heart ascend to God from the slopes of Mount Capreo, to win happiness for me and for Belgium." He prayed as if he expected everything from God; he acted as if success depended entirely on his own efforts.
In the struggles them maintained by the Belgian Catholics in favor of freedom of education, the nuncio's prudent and opportune intervention brought about happy results. In 1845 a very serious difference arose between the Jesuits and the University of Louvain. The cause of the dispute was the sudden founding of a special faculty of philosophy for laymen in the College de la Paix at Namur staffed by the Jesuits. Until that time the teaching of philosophy in Belgium had been reserved to the ecclesiastical seminaries for clerics and to the University of Louvain for the laity. On this subject the Belgian Catholics were divided into two factions. The bishops and a considerable number of the clergy took the university's part; while the laity in high stations and wielding great influence, even at Rome, were on the side of the Jesuits. The nuncio did all he could to calm the storm, and induced both parties to submit their claims to the supreme judgment of the Holy See. Gregory XVI asked for a complete report from the nuncio as well as a report from the Belgium hierarchy. Despite the eventual criticism of the nuncio, Archbishop Pecci's proposals and solution were followed, but under most discouraging circumstances. The solution was almost too simple to be believed by those who should have known better. Both schools, it was decided, should continue to exist simultaneously and thereby cause intellectual rivalry.
On the school question, the nuncio urged the bishops to obtain the support of the Catholic deputies and to use every constitutional means to establish or support religious education. When it was a question of encouraging studious youth, his assistance was assured. He made frequent visits to religious educational institutions, and especially to St. Michael's College in Brussels, where he took pleasure in conversing with the teachers and in stimulating ardor for the studies and emulation among the students...
Between 1843 and 1846, the archbishop made it a point to visit all the large cities in turn. He considered himself a Belgian by adoption, and to the end of his life Belgium was to exercise an attraction in his heart.
Although the clergy of Belgium were well trained, perhaps at the time better than anywhere else, Pecci still promoted the idea that a number of clergy should receive higher training at the very fountain of Christendom. He realized that the churches, the schools, the libraries, monuments, even ruins and memories, as well as papal personages are a Christian education. At an assembly of the Belgian bishops held at Mechlin in August, 1844, he laid the foundation for the establishment of a Belgian seminary in Rome.