politicians from both sides in Paris. The Act of Mediation was the result, which largely restored Swiss autonomy and introduced a Confederation of 19 cantons. Henceforth, much of Swiss politics would concern balancing the cantons' tradition of self-rule with the need for a central government. In 1815 the Congress of Vienna fully re-established Swiss independence, and the European powers recognised permanent Swiss neutrality. Swiss troops served foreign governments until 1860 when they fought in the siege of Gaeta. The treaty allowed Switzerland to increase its territory, with the admission of the cantons of Valais, Neuchâtel and Geneva. Switzerland's borders saw only minor adjustments thereafter. Federal state 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 less than a month, causing fewer than 100 casualties, most of which were through friendly fire. The Sonderbundskrieg had a significant impact on the psychology and society of Switzerland. The war convinced most Swiss of the need for unity and strength. Swiss from all strata of society, whether Catholic or Protestant, from the liberal or conservative current, realised that the cantons would profit more from merging their economic and religious interests. Thus, while the rest of Europe saw revolutionary uprisings, the Swiss drew up a constitution that provided for a federal layout, much of it inspired by the American example. This constitution provided central authority while leaving the cantons the right to self-government on local issues. Giving credit to those who favoured the power of the cantons (the Sonderbund Kantone), the national assembly was divided between an upper house (the Council of States, two representatives per canton) and a lower house (the National Council, with representatives elected from across the country). Referendums were made mandatory for any amendments. This new constitution ended the legal power of nobility in Switzerland. A single system of weights and measures was introduced, and in 1850 the Swiss franc became the Swiss single currency, complemented by the WIR franc in 1934. Article 11 of the constitution forbade sending troops to serve abroad, marking the end of foreign service. It came with the expectation of serving the Holy See, and the Swiss were still obliged to serve Francis II of the