Recorded history of the Grand Duchy of Luxembourg begins with the construction of Luxembourg Castle in 963. Around this fort a town gradually developed, which became the center of a small state, but important. County Luxembourg is raised to the rank of Duchy in 1354. In 1437 there was a crisis, the family heir to the throne. In the following centuries, Luxembourg's fortress was steadily enlarged and strengthened by those who occupied it, among others, the Bourbons, the Habsburgs, the Hohenzollerns and the French. Even after Napoleon's defeat in 1815, when the Congress of Vienna gave formal autonomy to Luxembourg, the country has become the subject of a dispute between Prussia and the Netherlands.