After Cyril died in 869 in Rome, Methodius continued their work on his own. He was appointed the Archbishop of Pannonia in 870, and from this period (873) comes the letter from the pope John VIII in which he invited Serbian prince Mutimir to accept the competence of Methodius, in an effort to expand the jurisdiction of Methodius' bishopric. This was in collision with the strivings of the Patriarchate of Constantinople to place the area under its authority. The appetites especially grew larger when in 870 the entire newly established Christian church in Bulgaria was subdued to Constantinople. This way, the areas of Belgrade and Morava valley came under the Byzantine religious jurisdiction, and the Metropolis of Morava was formed. First data on the church organization date from the 10th century. During the reign of Bulgarian emperor Peter I (927–969), the Bulgarian Patriarch and the Bulgarian Orthodox Church administered not only the bishoprics in the Morava valley, but also the Bishopric of Ras, the capital of Serbia, in the hinterland of the state. At the church Councils of Split, in 925 and 928, bishoprics in the Dalmatian cities of Dubrovnik and Kotor, bordering Serbian territories, are mentioned, so as the bishopric of Ston, which was part of Zachlumia. Ston was subordinated to the Archbishopric of Split.