Keep pulling the thread on Anthony Kaldellis.
During the war in the early 7th century, Persia conquered the Roman eastern provinces of Syria, Palestine, and Egypt.
The decades-long war between the Roman and Persian empires left both states destabilized and depleted of manpower and resources, which enabled the subsequent rapid Arab conquests.
Arab attempts to conquer Constantinople were defeated twice, in the 7th and 8th centuries, which was crucial for the survival of the Roman state.
In the 11th century, the Eastern Roman Empire faced a simultaneous three-front attack from the Normans in southern Italy, the Pechenegs from the north, and the Seljuk Turks from the east.
The final, irreversible decline of the Eastern Roman Empire began between 1300 and 1350, following the loss of Asia Minor to the Turks, a series of civil wars, and Serbian expansion.
During the Arab Spring in Egypt, President Hosni Mubarak was uncertain for approximately three weeks whether he could rely on the army to suppress protesters.
The Roman Empire and the Sasanian Persian Empire were engaged in a major war from approximately 602 to 628.
Persian Shah Khosrow II's policy during the war with Rome in the early 600s shifted from raiding for manpower to a strategy of permanent territorial conquest, aiming to extend the Persian Empire to the Mediterranean Sea.
A Roman civil war from 608 to 610, initiated by Heraclius, diverted Roman armies away from the Persian front, which provided a significant military advantage to the Persians.
The Roman Emperor Heraclius was aided in his final victory over the Persians by Turkish allies from Central Asia.
The Arab invasions of the Roman and Persian empires were strategically effective because they came from Arabia, a direction from which neither empire had prepared major defenses.
During the second Arab siege of Constantinople in the early 8th century, Emperor Leo III formed a military alliance with the Bulgars.