In Decades of Darkness, it was decided at the Congress of Vienna that Switzerland should become a monarchy. It was to be headed by the former King of Saxony (former since Prussia annexed Saxony by decision of the same Congress). After the alt-Sonderbund rebellion (which included the Protestants in support of the Old Confederacy), France and the German Confederation fought a war over the remains, which led to a series of principalities created in the German-speaking part (and absorbed into the German Confederation), and a rump Helvetic Republic created in the French-speaking part. After the Second Napoleonic Wars, Germany annexed the rump republic.