The forces of Zurich were defeated in the Battle of St. Jakob an der Sihl on 22 July 1443 and Zurich was besieged. 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 were wiped out, but inflicted such heavy losses on the French (8,000 killed) that the Dauphin decided to retreat.