The recorded history of Luxembourg begins with the acquisition of Lucilinburhuc (today Luxembourg Castle) situated on the Bock rock by Siegfried, Count of Ardennes in 963 through an exchange act with the abbey of St Maximin in Trier. Around this fort, a town gradually developed, which became the centre of a small state of great strategic value. In the 14th and early 15th centuries three members of the House of Luxembourg reigned as Holy Roman Emperors. In 1437, the House of Luxembourg suffered a succession crisis, precipitated by the lack of a male heir to assume the throne, which led to the territory being sold by Duchess Elisabeth to Philip the Good of Burgundy.
In the following centuries, Luxembourg's fortress was steadily enlarged and strengthened by its successive occupants, the Bourbons, Habsburgs, Hohenzollerns, and the French, among others. After the defeat of Napoleon in 1815, Luxembourg was disputed between Prussia and the Netherlands. The Congress of Vienna formed Luxembourg as a Grand Duchy in personal union with the Netherlands. Luxembourg also became a member of the German Confederation, with a Confederate fortress manned by Prussian troops.
The Belgian Revolution of 1830–1839 reduced Luxembourg's territory by more than half, as the predominantly francophone western part of the country was transferred to Belgium. Luxembourg's independence was reaffirmed by the 1839 First Treaty of London. In the same year, Luxembourg joined the Zollverein. Luxembourg's independence and neutrality were again affirmed by the 1867 Second Treaty of London, after the Luxembourg Crisis nearly led to war between Prussia and France. After the latter conflict, the Confederate fortress was dismantled.
The King of the Netherlands remained Head of State as Grand Duke of Luxembourg, maintaining personal union between the two countries until 1890. At the death of William III, the Dutch throne passed to his daughter Wilhelmina, while Luxembourg (at that
