In this period, the Saxon feud was fought, in which George, Duke of Saxony, allied with the Habsburgs, tried to subdue Frisia, the Ommelanden, and Groningen. The Frisians under the leadership of Jancko Douwama resisted and were supported by Edzard I, Count of East Frisia, and the inimitable Charles, Duke of Guelders. George of Saxony failed to conquer Groningen and was pushed back. When he held only a handful of cities (Leeuwarden, Harlingen en Franeker), he sold his rights to Charles of Habsburg in May 1515.