The Bosnian Church (Црква босанска) was a Christian church in medieval Bosnia and Herzegovina that was independent of and considered heretical by both the Catholic and the Eastern Orthodox hierarchies. Historians traditionally connected the church with the Bogomils, although this has been challenged and is now rejected by the majority of scholars. Adherents of the church called themselves simply Krstjani ("Christians") or Dobri Bošnjani, Usorani, Humljani... ("Good Bosnians, Usorans, Humlians..."). The church's organization and beliefs are poorly understood, because few if any records were left by church members and the church is mostly known from the writings of outside sources — primarily Catholic ones. The monumental tombstones called stećak that appeared in medieval Bosnia, as well as Croatia, Serbia, and Montenegro, are sometimes identified with the Bosnian Church. Christianization of the Slavs Christian missions emanating from Rome and Constantinople started pushing into the Balkans in the 9th century, Christianizing the South Slavs, and establishing boundaries between the ecclesiastical jurisdictions of the See of Rome and the See of Constantinople. The East–West Schism then led to the establishment of Catholicism in Croatia and most of Dalmatia, while Eastern Orthodoxy came to prevail in Serbia. Lying in-between, the mountainous Bosnia was nominally under Rome, but Catholicism never became firmly established due to a weak church organization and poor communications. Medieval Bosnia thus remained a "no-man's land between faiths" rather than a meeting ground between the two Churches, leading to a unique religious history and the emergence of an "independent and somewhat heretical church". Catholicism and Eastern Orthodoxy predominated in different parts of what is today Bosnia and Herzegovina; the followers of the former formed a majority in the west, the north, and in the center of Bosnia, while those of the latter were a majority in most of Zachlumia (present-day Herzegovina) and along Bosnia's eastern border.