Complex sentence: On 15 October 879, the bishops and nobles of the region around the rivers Rhône and Saône assembled in the Synod of Mantaille elected Boso king as successor to Louis the Stammerer, the first non-Carolingian king in Western Europe in more than a century.
Split into simpler sentences: On 15 October 879, the bishops and nobles of the region around the rivers Rhône and Saône assembled in the Synod of Mantaille. They elected Boso King and successor to Louis the Stammerer, the first non-Carolingian king in Western Europe in more than a century.