The Sonderbund war (German:Sonderbundkrieg) of November 1847 was a civil war in Switzerland. It ensued after the Sonderbund (meaning "separate alliance", in German) was created in 1845 in Switzerland as a league among seven Catholic and Conservative cantons, in order to protect their interests against a centralization of power.
The member cantons were Lucerne, Fribourg, Valais, Uri, Schwyz, Unterwalden and Zug. Some liberal Catholic cantons such as Ticino and Solothurn did not participate.
This alliance was concluded after the Radical Party had taken power in Switzerland and had, thanks to the majority of cantons, taken measures against the Catholic Church such as the closure of monasteries and convents in Aargau in 1841, and the seizure of their properties. When Lucerne, in retaliation, recalled the Jesuits the same year, groups of armed Radicals ("Freischler") invaded the canton. This caused a revolt, mostly because rural cantons were strongholds of ultramontanism.
The Sonderbund was in violation of the Federal Treaty of 1815, 6 of which expressly forbade such separate alliances, and the Radical majority in the Tagsatzung decided to dissolve the Sonderbund on October 21, 1847. The confederate army was raised against the members of the Sonderbund. The army was composed of soldiers of all the other cantons except Neuchel and Appenzell Innerrhoden (which had stayed neutral).
General Guillaume-Henri Dufour led the federal army of 100,000 and defeated the Sonderbund under Johann-Ulrich von Salis-Soglio in a campaign that lasted only from November 3 to November 29, and claimed fewer than a hundred victims. He ordered his troops to spare the injured, anticipating the formation of the Red Cross in which he participated a few years later.
Major actions were fought at Freiburg, Geltwil, Lunnern, Luzern, and finally at Gisikon, Meierskappel and Schfheim, after which Luzern capitulated on 24 November.
In 1848, a new Swiss Federal Constitution ended the almost-complete independence of the cantons and transformed Switzerland into a federal state. The Jesuits were banished from Switzerland. This ban was lifted on 20 May 1973, when 54.9% of the population and 16.5 cantons out of 22 accepted a referendum modifying the Constitution.