476 AD
The deposition of Romulus Augustulus by the Germanic chieftain Odoacer in 476 AD marked the end of the Western Roman Empire. With the collapse of secular authority, the Church became the primary institution preserving civilization in Europe. Bishops replaced Roman governors as the administrators of cities, and monasteries became centers of learning, agriculture, and social welfare.
The Church's role in preserving civilization during the Dark Ages cannot be overstated. Monasteries preserved classical literature, developed agricultural techniques, and provided education and medical care. The papacy emerged as a political force, with Pope St. Leo the Great negotiating with Attila the Hun in 452 and Pope St. Gregory the Great organizing the defense of Rome after 590. Key sources: Cassiodorus, Gregory the Great, Bede