Lord Enguerrand VII de Coucy, the thirty-five-year-old son-in-law of King Edward III of England and Philippa of Hainault, and a nephew of the Duke of Austria, claims (as the right of his mother, Katharina von Habsburg) the Swiss territory of Aargau held by his Habsburg cousin Duke Leopold III of Austria.

Having obtained both permission and gold from the French crown to gather a ten thousand-man army of French and English mercenaries, joined, at de Coucy’s invitation, by knights, he engages a number of Free Companies, including one led by Owain Lawgoch, to seize the Aargau.

Advancing across France to Alsace, the mercenary army ravages areas while marching south to Basel, crosses the Jura Mountains, and in November 1375 enters the lower Aargau, which forms part of a great tableland to the north of the Alps and the east of the Jura.

The mercenaries wear heavy cloaks with pointed hoods, called “Güglers” in Swiss-German, and become known by this name (as does the associated conflict).

Duke Leopold, installed comfortably at Breisach to the north, refuses to engage de Coucy’s invaders and instead orders a systematic destruction of Aargau.

This leaves no villages, people, booty, or food for the invaders, but also earns Leopold the intense enmity of his Swiss subjects.