The County of Luxemburg (French: Luxembourg; Luxembourgish: Lëtzebuerg) was a State of the Holy Roman Empire. It arose from medieval Lucilinburhuc ("Little Fortress") Castle in the present-day City of Luxembourg, purchased by Siegfried, Count of the Ardennes in 963. His descendants of the began to call themselves Counts of Luxembourg from the 11th century onwards. The House of Luxembourg, a cadet branch of the Dukes of Limburg, became one of the most important political forces of the 14th century, contending with the House of Habsburg for supremacy in Central Europe.