Zurich retaliated by making an alliance with Frederick III, Holy Roman Emperor of the house of Habsburg.
Frederick appealed to Charles VII of France to attack the confederates and the latter sent a force of about 30,000 Armagnac mercenaries under the command of the Dauphin via Basel to relieve the city.
In the Battle of St. Jakob an der Birs near Basel on 26 August 1444, a blocking force of roughly 1,600 Swiss confederates was defeated, but inflicted such heavy losses on the French (2,000 killed) that the Dauphin decided to retreat.
The confederacy and the Dauphin concluded a peace in October 1444, and his mercenary army withdrew from the war altogether.
The significance of the war is that it showed that the confederation had grown into a political alliance so close that it no longer tolerated separatist tendencies of a single member.