There is debate about when Christianity was first introduced; it was no later than the 4th century, probably much earlier. According to Bede, missionaries were sent from Rome by Eleutherius at the request of the chieftain Lucius of Britain in 180 AD, to settle differences as to Eastern and Western ceremonials, which were disturbing the church. There are traditions linked to Glastonbury claiming an introduction through Joseph of Arimathea, while others claim through Lucius of Britain. By 410, during the Decline of the Roman Empire, Britain was left exposed by the end of Roman rule in Britain and the withdrawal of Roman army units, to defend the frontiers in continental Europe and partake in civil wars. Celtic Christian monastic and missionary movements flourished: Patrick (5th-century Ireland) and in the 6th century Brendan (Clonfert), Comgall (Bangor), David (Wales), Aiden (Lindisfarne) and Columba (Iona). This period of Christianity was influenced by ancient Celtic culture in its sensibilities, polity, practices and theology. Local "congregations" were centred in the monastic community and monastic leaders were more like chieftains, as peers, rather than in the more hierarchical system of the Roman-dominated church.