Wilhelm Ludwig died in 1640, and his wife, now Countess, and his son Johann Ludwig II returned to Saarbrücken. The Peace of Westphalia restored the lands of the House of Nassau. Johann Ludwig II rose to Count at the death of his mother. Because of the dispute with Lorraine, The House of Nassau had to abandon their capital of Bouquenom (Bockenheim) and the city of Sarrewerden, which had belonged to the Bishopric of Metz, which was now owned by Lorraine. They built on the opposite side of the river Saar, a new city: Neu-Saarwerden. The County had suffered from the Thirty Years' War. Count Gustav Adolph set about rebuilding the war-ravaged county, bringing back refugees, and recruiting settlers for agriculture and skilled workers. Later, Gustav became a prisoner-of-war of France and France occupied Saarwerden. After the Treaty of Ryswick in 1697, his lands were returned to Ludwig Crato I and he became Regent. He was considered a good ruler, as he could keep his country out of further wars. He organized the administration of justice and the state finances. He showed benevolence and reorganized the school system.
