A significant number of Bosnians converted to Islam after the conquest by the Ottoman Empire in the second half of the 15th century, giving it a unique character within the Balkan region. This conversion appears to have been not sudden but a gradual process based on various rules imposed by the Ottomans — it took more than a hundred years for the number of Muslims to become the majority religion. The general view among scholars is that the Islamization of the Bosnian population was not the result of violent methods of conversions but was, for the most part, peaceful and voluntary.
Several factors appear to have been behind this process. Most important was that Christianity had relatively shallow roots in Bosnia prior the Ottoman domination. Bosnia lacked a strong Christian church organization to command a strong following—the result of a scarcity of priests and competition among the Orthodox and Roman Catholic Churches and the indigenous and schismatic Bosnian Church, which collapsed shortly before the Ottomans arrived. This left most Bosnians religiously unengaged and receptive to the appeal of Islam’s sophisticated and dynamic institutions. This receptiveness was aided by the development among many Bosnians of a kind of folk Christianity centered on various practices and ceremonies that was adaptable to a form of folk Islam popular at the time of the invasion.
Always on a purely religious ground, it is also said, by the orientalist Sir Thomas Arnold for instance, that because of Bogomilism, a major dualistic heresy in the region at the time, oppressed by the Catholics and against whom Pope John XXII even launched a Crusade in 1325, the people were more receptive to the Turks. In fact, in the Bogomilian tradition, there were several practices that resembled Islam: they rejected the veneration of the Virgin Mary, repudiated the Cross as a religious symbol, they considered it as idolatry to bow down before religious images, relics or saints, and even prayed five times a day (reciting the Lord's Prayer.)