About 999, the last king of Upper Burgundy, Rudolph III, granted the Countship of Valais to Bishop Hugo (998-1017); this union of the spiritual and secular powers made the prince-bishop the most powerful ruler in the valley of the Upper Rhone, the region called the Valais. Taking this donation as a basis, the bishops of Sion extended their secular power, and the religious metropolis of the valley became also the political centre. However, the union of the two powers was the cause of violent disputes in the following centuries. For, while the spiritual jurisdiction of the bishop, as Bishop of Sion, extended over the whole valley of the Rhone above Lake Geneva, the Countship of Valais included only the upper part of the valley, reaching to the confluence of the Trient and the Rhone. The attempts of the bishops of Sion to carry their secular power farther down the Rhone were bitterly and successfully opposed by the abbots of Saint-Maurice, who had obtained large possessions in Lower Valais.