<Ul> <Li> The crisis of Late Antiquity, which saw invasions by the Visigoths, Huns, Alans, and Vandals across both the Rhine and Danube frontiers, sweeping through most of Europe </Li> <Li> 602 - Start of the Byzantine--Sassanid War of 602--28, which exhausted the Empire's resources and contributed to major territorial losses during the Muslim conquests of the 7th century . </Li> <Li> The crisis of the 7th century, which saw Muslim conquest of the Levant and the Arab - Byzantine Wars <Ul> <Li> 634--Start of the Byzantine - Arab Wars </Li> <Li> 636 - The Battle of Yarmouk </Li> </Ul> </Li> <Li> The crisis of the 11th century, which simultaneously saw the Norman conquest of southern Italy, the Pechenegs (in the Crimea and the Balkans), and the Seljuk invasion of Asia Minor and the devaluation of the nomisma <Ul> <Li> 1025--Death of the soldier - emperor Basil II </Li> <Li> 1071--The Battle of Manzikert </Li> <Li> 1176 - The Battle of Myriokephalon </Li> <Li> 1180--Death of Manuel I Komnenos </Li> <Li> 1185--Demise of the Komnenos dynasty </Li> </Ul> </Li> <Li> The crises of the 13th century, which followed the Sack of Constantinople and partitioning of the empire by the Fourth Crusade <Ul> <Li> 1204--The Sack of Constantinople by the Fourth Crusade </Li> </Ul> </Li> <Li> The final decline during the Byzantine--Ottoman Wars . </Li> </Ul> <Li> The crisis of Late Antiquity, which saw invasions by the Visigoths, Huns, Alans, and Vandals across both the Rhine and Danube frontiers, sweeping through most of Europe </Li> <Li> 602 - Start of the Byzantine--Sassanid War of 602--28, which exhausted the Empire's resources and contributed to major territorial losses during the Muslim conquests of the 7th century . </Li> <Li> The crisis of the 7th century, which saw Muslim conquest of the Levant and the Arab - Byzantine Wars <Ul> <Li> 634--Start of the Byzantine - Arab Wars </Li> <Li> 636 - The Battle of Yarmouk </Li> </Ul> </Li>

What factors led to the decline of the byzantine empire