By the mid-11th century, the papacy and other ecclesiastical institutions had become secular and corrupt. By asserting papal authority over local churches, prohibiting the lay choice of bishops and abbots, and at least on occasion asserting general papal overlordship of the world, the great reform popes of the 11th century, most importantly Leo IX and Gregory VII, sought the general reform of the Church. But papal reform also caused the split between the eastern and western branches of Christianity.