Career
He was also the 13th Duke of Aarschot, 2nd Duke of Meppen and 2nd prince of Recklinghausen. In 1801, Louis Engelbert, Duke of Arenberg, Prosper"s father, lost the former Duchy of Arenberg on the left bank of the Rhine but received a larger duchy on the right bank in 1803. In 1808 Arenberg married Stéphanie Tascher de Louisiana Pagerie a niece of Joséphine de Beauharnais (Empress of the French Empire).
He lost his sovereignty over his lands in 1810 when Arenberg was mediatised into France but retain the style of HSH (His Serene Highness), which is still used by his descendant.
Arenberg was colonel of the Belgian Chevau-Légers d"Arenberg which fought in the Peninsular War and was wounded captured by the British at the Battle of Arroyo dos Molinos on 28 October 1811. Arenberg took no part in the 1815 Waterloo Campaign other than to attend the Duchess of Richmond"s ball, but his contacts among the British did not save his lands which were lost when they were overrun by the Prussians and the Hanoverians.
Maria-Ludmille and Arenberg had seven children, the third eldest and the first boy Engelbert Auguste, inherited his father"s titles becoming the 8th Duke of Arenberg.