Islam emerged on the Arabian Peninsula in the seventh century. The religion won many converts and expanded dramatically. They reached Western Europe by the eighth century. Meanwhile, the Byzantine Empire fought a destructive war with the Sassanid Empire. By the end of the conflict, the Sassanid Empire collapsed and the Byzantines were exhausted. These factors combined with Byzantine religious policy to fuel Islam’s dramatic spread. Essentially, no power strong enough existed to blunt the Islamic tide.
The Sassanid Empire launched an unprovoked attack upon the neighboring Byzantines in 602. The conflict between Rome’s successor state and the Persian-based invaders lasted 26 years. The Persians held the advantage early on. In fact, they captured Mesopotamia, the Caucus, Syria, Egypt, Palestine and invaded the Byzantine heartland. They arrived at Constantinople to deliver the knock out blow, but failed to eliminate the rival empire. In 622, Byzantine Emperor Heraclius launched a counter-offensive. In an amazing turnabout, Heraclius defeated the Persians and ended the war.
In the same year Heraclius assumed power, Muhammad received his first revelation. Around the same time the Byzantines eliminated the Sassanid Empire, Muhammad claimed Mecca for Islam. The Prophet died in 632, but the Muslim expansion had just begun. The Sassanid Empire might have contained the Muslims had it not expired. The jihadists conquered Persia in 644.
Although the war lasted 26 years, the conflict between the Byzantines and Sassanids lasted 400. The Byzantines survived victorious, but weakened. The Islamic Arabs and Byzantines first clashed in 629. The Byzantines easily rebuffed the first assault, but soon found themselves overwhelmed. The Sassanid War left the empire’s resources depleted and army weakened. Additionally, the Byzantines had little experience fighting the Arabs. Their military history was devoid of information on the new enemy. The Muslims won a dramatic victory at Yarmouk in 636. By 641, most of Egypt had fallen to Islam.
The Byzantines unwittingly assisted Islam’s expansion through religious policy. Heraclius attempted to heal the schism between eastern and western Christianity. Instead, he provided willing converts to Islam. The emperor hoped to work a compromise, but it was rejected by all sides. Additionally, his efforts came across as heavy handed. As a result, many Christians on the front lines had little problem converting to Islam, which seemed less intrusive.
The lack of ideological or religious conviction combined with weakened imperial states allowed the early Muslim conquests. People converted so they could live their lives in peace. Meanwhile, the Byzantines and Sassanids proved unable to stop the Islamic wave. The Muslims reached Hispania by the early eighth century. Western Europe lacked a strong entity to oppose them. However, the Franks under Charles “The Hammer” Martel finally stopped the invaders in 732. This marked the last Islamic threat to Western Europe until the 21st century. However, it did not stop their expansion in the east. The Byzantines fell in 1453. Islamic expansion finally ended in the late 17th century.
Islam expanded at an amazing rate from the seventh through seventeenth centuries. The Byzantine-Sassanid War literally opened the door for Muhammad’s followers. The Sassanid Empire collapsed and the Byzantines left in a weakened position. As a result, no military force stood to oppose the Muslims until the Franks under Charles Martel. A strong Sassanid Empire probably would have snuffed out the Muslims. A strong Byzantine Empire probably would have blunted the Islamic expansion. However, their imperial rivalry led to unintended consequences and their mutual destruction.