Historic map (undated) of Luxembourg city's fortifications
Photograph of the fortress of Luxembourg prior to demolition in 1867
The recorded history of Luxembourg begins with the acquisition of Lucilinburhuc
Luxembourg Castle) situated on the
Bock rock by
Siegfried, Count of Ardennes, in 963 through an exchange act with
St. Maximin's Abbey, Trier.
 Around this
town gradually developed, which became the centre of a 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 territories being sold by Duchess
Philip the Good of
In the following centuries, Luxembourg's fortress was steadily enlarged and strengthened by its successive occupants, the
Hohenzollerns and the French.
Napoleon in 1815, Luxembourg was disputed between
Prussia and the
Congress of Vienna formed Luxembourg as a
Grand Duchy within the German Confederation. The Dutch king became, in
personal union, the grand duke. Although he was supposed to reign the grand duchy as an independent country with an administration of its own, in reality he treated it similarly to a Dutch province. The
Fortress of Luxembourg was manned by Prussian troops for the German Confederation.
 This arrangement was revised by the 1839
First Treaty of London, from which date Luxembourg's full independence is reckoned.
Luxembourg City: The Passerelle, also known as the viaduct or old bridge, overseeing the
river valley; it opened in 1861.
At the time of the
Belgian Revolution of 1830–1839, and by the 1839 Treaty establishing full independence, Luxembourg's territory was reduced by more than half, as the predominantly
western part of the country was transferred to
Belgium. In 1842 Luxembourg joined the German Customs Union (
 This resulted in the opening of the German market, the development of
Luxembourg's steel industry, and expansion of
Luxembourg's railway network from 1855 to 1875, particularly the construction of the Luxembourg-
Thionville railway line, with connections from there to the European industrial regions.
 While Prussian troops still manned the fortress, in 1861, the
Passerelle was opened, the first road bridge spanning the
Pétrusse river valley, connecting the
Ville Haute and the main fortification on the Bock with
Luxembourg railway station, opened in 1859, on the then fortified Bourbon plateau to the south.
Luxembourg Crisis of 1866 nearly led to war between Prussia and France, the Grand Duchy's independence and neutrality were again affirmed by the 1867
Second Treaty of London, Prussia's troops were withdrawn from the Fortress of Luxembourg, and its Bock and surrounding fortifications were dismantled.
King of the Netherlands remained
Head of State as
Grand Duke of Luxembourg, maintaining a personal union between the two countries until 1890. At the death of
William III, the throne of the Netherlands passed to his daughter
Wilhelmina, while Luxembourg (then restricted to male heirs by the
Nassau Family Pact) passed to
Adolph of Nassau-Weilburg.
At the time of the
Franco-Prussian war in 1870, despite allegations about French use of the Luxembourg railways for passing soldiers from
Metz (then part of France) through the Duchy, and for forwarding provisions to Thionville, Luxembourg's neutrality was respected by
Germany, and neither France nor Germany invaded the country.
 But in 1871, as a result of Germany's victory over France, Luxembourg's boundary with
Lorraine, containing Metz and Thionville, changed from being a frontier with a part of France to a frontier with territory annexed to the
German Empire as
Alsace-Lorraine under the
Treaty of Frankfurt. This allowed Germany the military advantage of controlling and expanding the
Frontier with German Empire's Alsace-Lorraine, from 1871 to 1918
In August 1914,
Imperial Germany violated Luxembourg's neutrality in the war by invading it in the war against France. This allowed Germany to use the railway lines, while at the same time denying them to France. Nevertheless, despite the
German occupation, Luxembourg was allowed to maintain much of its independence and political mechanisms.
In 1940, after the outbreak of
World War II, Luxembourg's neutrality was again violated when the
Nazi Germany entered the country, "entirely without justification".
 In contrast to the First World War, under the
German occupation of Luxembourg during World War II, the country was treated as German territory and informally annexed to the adjacent province of the
Third Reich. A
government in exile based in London supported the
Allies, sending a small group of volunteers who participated in the
Normandy invasion. Luxembourg was liberated in September 1944, and became a founding member of the
United Nations in 1945. Luxembourg's neutral status under the
constitution formally ended in 1948, and in 1949 it became a founding member of
In 1951, Luxembourg became one of the six founding countries of the
European Coal and Steel Community, which in 1957 would become the
and in 1993 the
European Union. In 1999 Luxembourg joined the
Eurozone. In 2005, a
referendum on the EU treaty establishing a constitution for Europe was held.