In the early 13th century, Hungarian–Cuman relations were again tense, prompting Andrew II to create a system of border defenses, which included granting the border region of Burzenland to the Teutonic Order. This group streamlined the first effort to Christianize Cuman communities living outside the Pannonian Basin. The Cumans were themselves attacked and defeated by the Mongol Empire; most Cumans fled to Hungary, the Bulgarian Empire, and the Byzantine Empire. By the 1220s, many were concentrated to the east of Hungary, in areas later known as Moldavia and Bessarabia. Their conversion to Christianity began here, under Hungarian auspices, leading to the establishment of a Cumanian Catholic Bishopric; some members of the tribes had converted to rival Eastern Orthodoxy, or to Bogomilism, and had to be brought back to Catholicism. At that stage, an untold number of Cumans in Hungary were converts to Islam.