The restoration of power to the patriciate was only temporary. After a period of unrest with repeated violent clashes such as the Züriputsch of 1839, civil war (the Sonderbundskrieg) broke out in 1847 when some Catholic cantons tried to set up a separate alliance (the Sonderbund). The war lasted for less than a month, causing fewer than 100 casualties, most of which were through friendly fire. Yet however minor the Sonderbundskrieg appears compared with other European riots and wars in the 19th century, it nevertheless had a major impact on both the psychology and the society of the Swiss and of Switzerland.

What did Catholic cantons attempt to set up which caused a civil war in 1839?