In 1236–37, Aymon,
Baron of Faucigny, made himself protector of the priory of
Chamonix despite the fact that the count of Geneva had a prior right. The ensuing war, in which Aymon's son-in-law,
le Petit Charlemagne, was captured by William's son
Rudolf, resulted in Genevan defeat, for on 13 May 1237 William II was forced to accept the judgement of Peter's brother,
Amadeus IV, Count of Savoy, condemning him to an
indemnity of 20,000
marks and the cession of the strategic
Castle Arlod on the
Rhône near its confluence with the
Valserine, which commanded the approach to the
Lyonnais. In 1250 William II went to war again against
le Petit Charlemagne in an effort to check his expansion in the
pays de Vaud. Although no contemporary source describes the course of the war, it is evident that William was defeated. He lost the fortress of
Les Clées, which commanded the pass into
Burgundy, and that of Bourg-du-Four in the centre of
Geneva. He was also forced to accept the arbitration of Peter's brother,
Philip, Archbishop of Lyon, who in turn imposed a
"Carthagenian settlement" on 28 June: the count was forced to cede to Peter a large
gagerie as security against the payment of an indemnity set at 10,000 marks, which was half of the indemnity ordered in 1237. The
gagerie comprised the castles of Geneva, Les Clées,
Charousse,
Ballaison,
Rue; the homages of the
Count of Gruyére and of the lords of
Langin,
Oron and
Vufflens; and all the jurisdictions William possessed in the
Pays de Vaud, the
Chablais and in
Faucigny, between the
Arve and the
Dranse and between the
Cluse de Gex and the
Pont de Bargen. By this concession the once powerful county of Geneva was reduced to little more than the
Genevois. The archbishop further intervened in the dispute between William and Peter over Arlod, deciding that it should remain in Peter's possession until an inquiry could determine if it pertained to the sire of
Gex or to the prior of
Nantua, who happened at that time to be
Boniface, brother of Peter and Philip. ==Marriage and children==