During 1383-1384, the expansion of the Old Swiss Confederacy collided with Austrian interests. The interests of Austria were further undermined in the Pact of Constance, a union of Zürich, Zug, Solothurn and 51 cities of Swabia. In 1385, there were various attacks, without formal declaration of war or central organization, by forces of Zürich, Zug and Lucern on the Austrian strongholds of Rapperswil, Rothenburg Cham and Wolhusen.