Prior to the arrival of Christianity in the 5th century, the Irish followed Celtic religious practices that had been in place for thousands of years. Like indigenous religious traditions in many parts of the world, they were focused on the forces of nature. Rituals sought to placate gods who could unleash nature’s destructive forces or ensure favorable conditions for good harvests; celebrations marked the solar cycle of seasons. Irish religious practice was also influenced by Roman religion after the Roman conquest of Britannia in 43 CE. Druids were the religious authorities in this system, seen as intermediaries between humans and the other world – they can analogously be described as priests. What little is known about pre-Christian religion in Ireland comes from Greco-Roman sources and later Christian texts. When St. Patrick and other missionaries began to spread Christianity in Ireland, they discovered that many Christian traditions could be overlaid with the indigenous traditions that they encountered. This brought the graces of Celtic spirituality into the fold of the Christian tradition and led to a gradual, non-violent conversion process in Ireland, in contrast to the intertwined conquest and conversion that took place in some other parts of the world.