How was the Swiss union formed on the territory of Germany?

The Swiss Union was formed in 1291. It includes three katons: Schwyz, Unterwalden, Uri. The purpose of the union is to fight the ss with the Austrian Habsburgs. This unification made it possible to increase the power of the army, after which others followed the example of these catones and began to join the alliance. In terms of its territorial and political structure, the union was a confederation (sovereign countries are united on equal terms), when only the foreign policy and defense of the state become common.