Many religious groups often supply scripture and reading material, organize programs and worship, and train chaplains for work in prisons. Members of religious groups also engage in missionary activity, as there have been many instances of conversion throughout history. For instance, one of the earliest introductions of Islam into Eastern Europe was through the work of an early 11th century Muslim prisoner who was captured by the Byzantines during their war against Muslims. The Muslim prisoner was brought into the territory of the Pechenegs where he taught and converted individuals to Islam. In the United States, early colonists originated the concept of the penitentiary as a place where inmates would demonstrate their penance and remorse for their crimes through prayer and reflection.