The First Hundred Years After Mohammed

In just over one hundred years following the death of Mohammed in 632, the Arab followers of the Prophet had subjugated a territory with an east-west expanse greater than the Roman Empire, and they accomplished it in about half the time. By the mid-eighth century, Arab armies had conquered the thousand-year-old Persian Empire, reduced the Byzantine Empire to little more than a city-state based around Constantinople, and destroyed the Visigoth kingdom of Spain. The cultural and linguistic effects of this early Islamic expansion still reverberate today.

- from the inside flap of the book,
The Great Arab Conquests by Hugh Kennedy

Many conquerors have come and gone, but the Islamic conquest had a devastating impact on the world — arguably a more devastating impact than any conquest before or since, including Alexander the Great, Hannibal, and Ghengis Khan — because it wasn't merely a matter of the new conquerer gaining tribute. The Islamic conquerors took everything from the newly conquered: money, language, culture, traditions, wives, children, values. Everything. The nature of Islam is that it replaces cultures wherever it gets a foothold.