The siege of Luxembourg, in which Louis XIV of France (husband of Maria Theresa of Spain) laid siege to the Spanish-controlled Fortress of Luxembourg from 27 April to 7 June 1684, was the most significant confrontation between France and Spain of the War of the Reunions. The action caused alarm among France's neighbours and resulted in the formation of the League of Augsburg in 1686. In the ensuing war France was forced to give up the duchy, which was returned to the Habsburgs by the Treaty of Ryswick in 1697.