Bilhorod, Yuriy (1032), Chełm (1235) and Tver (1271). There also were dioceses in Zakarpattia and Tmutarakan. In 1261 the Sarai-Batu diocese was established. Foreign relations Turkic peoples From the 9th century, the Pecheneg nomads began an uneasy relationship with Kievan Rus'. For over two centuries they launched sporadic raids into the lands of Rus', which sometimes escalated into full-scale wars (such as the 920 war on the Pechenegs by Igor of Kiev reported in the Primary Chronicle), but there were also temporary military alliances (e.g., the 943 Byzantine campaign by Igor). In 968, the Pechenegs attacked and besieged the city of Kiev. Some speculation exists that the Pechenegs drove off the Tivertsi and the Ulichs to the regions of the upper Dniester river in Bukovina. The Byzantine Empire was known to support the Pechenegs in their military campaigns against the Eastern Slavic states. Boniak was a Cuman khan who led a series of invasions on Kievan Rus'. In 1096, Boniak attacked Kiev, plundered the Kiev Monastery of the Caves, and burned down the prince's palace in Berestovo. He was defeated in 1107 by Vladimir Monomakh, Oleg, Sviatopolk and other Rus' princes. Mongols The Mongol Empire invaded Kievan Rus' in the 13th century, destroying numerous cities, including Ryazan, Kolomna, Moscow, Vladimir and Kiev. Giovanni de Plano Carpini, the Pope's envoy to the Mongol Great Khan, traveled through Kiev in February 1246 and wrote: When this was done, they [the Mongols, "Tartari")] marched against Rus', and made great havoc in it, destroyed cities and forts, and killed people. They besieged Kyiv, the metropolis of Rus', for a long time, and finally took it and killed its citizens. From there, while passing through that land, we found innumerable skulls and bones of dead men, lying on the ground. For the city had been very large and populous, but now it seems reduced to nothing: for hardly more than two hundred houses remain, whose inhabitants are also held in absolute servitude.Besides the looting and loss of lives, the Mongol invasions led to demands of tribute (vykhod), while expropriations caused villages to be abandoned. The Russians had to provide sustenance and lodgings for Mongol envoys, although tax exemptions were awarded to villages that had to bear the brunt of these costs. Byzantine Empire Byzantium quickly became the main trading and cultural partner for Kiev, but relations were not always friendly. One of the largest military