Secession from Belgium and dissolution of the fortress.

In November 1830, the Congress of London ordered an armistice between the Netherlands and breakaway Belgium. A first peace treaty was rejected by the Belgians, the second by the Dutch government. In 1839, a new Treaty of London came and was approved by both parties.
The main goal was to prevent this conflict from growing into a new European war. On December 20, they declared Belgium's independence. In January 1831, the Conference decided that Belgium would be neutral in perpetuity and that the pre-1790 borders would be restored.
It was further agreed that William 1 would join the German Confederation as Duke of Limburg, so that this Confederation would receive compensation for the withdrawal of the part of the Grand Duchy of Luxembourg assigned to Belgium. On Aug. 16, 1839, William 1 proposed to the Federal Assembly that the entire territory assigned to him in the former province of Limburg, with the exception of the fortresses of Maastricht and Venlo, be included in the German Confederation as the Duchy of Limburg.
William 1 added the newly acquired territory to the Kingdom of the Netherlands. So the fortresses of Maastricht and Venlo were given a somewhat special status because they were supposed to control the Meuse, and the Prussians in particular wanted to keep a finger in the pie there. Hence also the federal contingent Limburgse Jagers and the fact that Limburg became a duchy in addition to being a province. Experts in the field actually assumed that in case of French aggression both fortresses would immediately receive a Prussian garrison. Even in Luxembourg there was such a strange thing going on, there was a mixed Prussian and Dutch garrison.

So wasn't there a fierce battle over Maastricht between sympathizers for joining Belgium and William 1 faithful? It is true that in 1830 there was a group of intellectuals who chose Belgium, but that group was in the minority. Trade and industry sided with the Northern Netherlands and thus with William I. The church remained aloof. General Bernard Dibbets managed to renew the garrison with a gentle hand. Thus, there was never any real confrontation between the two groups.
Maastricht again became a remote frontier fortress after its secession from Belgium (1839), which modern warfare wrote off as indefensible not much later.
The Dutch province of Limburg has existed in its present form as a political and institutional unit since 1839. Yet it was not until 1967 that the province's centennial was celebrated, because the Treaty of London of May 11, 1867, formally ended the curious situation in which Limburg was both
was an integral part of the Kingdom of the Netherlands, as well as of the German Confederation. This dual political relationship is evident from article 1 of the 1840 Constitution. This article stated that the Kingdom of the Netherlands would consist of ten provinces, "provided that the Duchy of Limburg, subject to the relations of that Duchy, with the exception of the fortresses of Maastricht and Venlo and of their circles, to the German Confederation." Only after leaving the German Confederation was Limburg apparently considered a full-fledged province of the Netherlands!

In view of the concentration of national defense behind the Dutch Waterline, Maastricht was abolished as a fortified stronghold by royal decree on May 29, 1867. The removal of the Maastricht, Venlo and Luxembourg fortresses in 1867 was thus closely linked to the larger European policy. Large portions of the fortress fell prey to industrial development and residential construction. Thanks to chance, important portions of the fortification escaped the demolition hammer. The beginning of the restoration of the fortress took place in 1881 by the unsurpassed referendaire Victor de Stuers (founder of the preservation of monuments in our country) with the restoration of the medieval character of the Helpoort and its surroundings. The selfless efforts of the many volunteers of the Maastricht Fortress City Foundation and the Menno van Coehoorn Foundation as well as the increasing interest in fortress history by residents and thousands of visitors testify to an increasing appreciation for this sector of historical cultural heritage.