The present-day state of Luxembourg first emerged at the Congress of Vienna in 1815. The Grand Duchy, with its powerful fortress, became an independent state under the personal possession of William I of the Netherlands with a Prussian garrison to guard the city against another invasion from France. In 1839, following the turmoil of the Belgian Revolution, the purely French-speaking part of Luxembourg was ceded to Belgium and the Luxembourgish-speaking part (except the Arelerland, the area around Arlon) became what is the present state of Luxembourg.