Paulicians, in Christian church history, heretical sect in the East, with a basis in ethical dualism and growing probably out of opposition to the hierarchical structure of the church. Their founder was Constantine of Mananali (about the 7th century AD), who established his first congregation in Armenia about 660. He was put to death by order of the Byzantine emperor Constantine IV, but the sect survived. In the 9th century the Paulicians allied themselves with the Saracens against the Byzantine Empire and reached their greatest strength. Although defeated decisively by the Byzantine emperor Basil I in 872, they remained a military power, notably in Thrace (now in Bulgaria), during the next century. The sect fused there with the Bogomils, who survived into the 15th century, and some present-day Armenian sects may be derived from the Paulicians. The sect rejected, in addition to church hierarchy, the Old Testament and parts of the New Testament, as well as the sacraments of baptism, the Eucharist, and marriage. Paulicians were also iconoclasts.