The province of Katai [Cathay] and Ong, which seems to have replaced the old T'ang dynasty province of Beth Sinaye, covered northern China and the country of the Christian Ongut tribe around the great bend of the Yellow River. The metropolitans of Katai and Ong probably sat at the Mongol capital Khanbaliq. The patriarch Yahballaha III grew up in a monastery in northern China in the 1270s, and the metropolitans Giwargis and Nestoris are mentioned in his biography.Budge, The Monks of Kublai Khan, 127 and 132 Yahballaha himself was consecrated metropolitan of Katai and Ong by the patriarch Denha I shortly before his death in 1281.Bar Hebraeus, Ecclesiastical Chronicle, ii. 452
