Through it's existence, the Byzantine empire faced many enemies some of them were weak and the other were mighty the byzantines managed to survive by military power or diplomacy or any other way they could find.
from the foundation,first decline,Justinan reconquest,Arab conquest,fighting for survive,the revival under Basil I,Turks arrival and settlement,decline's arrested under Comnenus dynasty, Crusades,Fragmentation,recover Constantinpole to the last stand against the Turks,the empire showed a unique act in whole history.
What is your opinion?who was the strongest rival?who are the most strong rival that the byzantine had tactical difficulties in warfare to deal with him?