son, William Louis "Us Heit" (West Frisian for "our father") was Stadholder of Friesland, Groningen, and Drenthe, a General in the Dutch States Army and the chief lieutenant of his cousin Prince Maurice of Nassau, in their innovations in military strategy and organization, victories in the field, and governing of the Dutch Republic. Second House of Nassau-Dietz The counts (later princes in 1650) of Nassau-Dietz continued their service to the Dutch Republic. After the death of William Louis (see Second House of Nassau-Dillenburg) they were usually elected Stadholder of Friesland, Groningen, and Drenthe. They also served as senior Generals in the Dutch States Army. In his will, William III appointed John William Friso as his heir in The Netherlands (his lordships being his property to dispose of by law) as well as his heir to the principality of Orange, the principality being a sovereign state, and so his right to appoint his successor. This was contested by the House of Hohenzollern, Kings of Prussia, and not finally settled until the mid 18th century. In any case, the succession was in the title only, as Louis XIV of France had conquered the actual territory. Second House of Nassau-Hadamar In 1620, the younger line of Nassau-Hadamar was split off from Nassau-Dillenburg, as shown below. John Louis, the first count, was a diplomat, who tried to protect his county from the ravages of the Thirty Years War. In 1647, for his efforts in bringing about peace between Spain and the Netherlands, King Philip IV of Spain appointed him a knight in the Order of the Golden Fleece. In addition, as a special thanks for his role in establishing the Peace of Westphalia, he was elevated to the rank of prince in 1650 by Emperor Ferdinand III. He did convert to Catholicism, so that Hadamar was Catholic after that. Second House of Nassau-Siegen In 1606 the younger line of Nassau-Siegen was split off from the House of Nassau-Dillenburg for John VII "the Middle". As Dillenburg eventually was inherited by a younger son of John VI (see below), the line of Nassau-Siegen became the elder line of the Ottonian House of Nassau. After John VII of Nassau-Siegen died in 1628, the land was divided: His eldest son, John VIII "the Younger", had converted to Catholicism and joined the Spanish Army. This caused a rivalry between him and his brother John Maurice below. The result was