In Europe, the late 9th century saw the steady decline of the Carolingian dynasty. Following the Treaty of Verdun (843), the empire was split, but by the 880s, the failure of to unify the Frankish realms against external threats led to a permanent fracturing. This vacuum allowed local lords to gain power, laying the groundwork for the feudal system . From this chaos, the distinct foundations of modern France and Germany began to emerge, while the Kingdom of Italy remained a contested prize for various claimants. 2. The Viking Age and the Rise of Wessex
This period was the height of the Viking Age. In the British Isles, the "Great Heathen Army" landed in the 860s, systematically toppling the Anglo-Saxon kingdoms of East Anglia, Mercia, and Northumbria. However, the tide turned under of Wessex. Following his victory at the Battle of Edington in 878, Alfred secured the Treaty of Wedmore, which established the "Danelaw" but preserved a sovereign English state. His reforms in education, law, and military defense (the burgh system) made him the "architect of England." 3. The Islamic World: The Abbasid Decline [851-900]
The years 851–900 were a time of "reordering." While the great centralized states of the early medieval period—the Carolingians, the Abbasids, and the Tang—began to fail, the seeds of new nations were planted. Whether through Alfred’s defense of Wessex, the Byzantine cultural expansion, or the Samanid patronage of Persian culture, this half-century defined the political and religious boundaries that would shape the next millennium of history. In Europe, the late 9th century saw the