In 632 CE, the Prophet Muhammad died in Medina, leaving behind a community of perhaps 100,000 followers confined to the Arabian Peninsula. One hundred years later, the Islamic Caliphate ruled an empire larger than Rome at its peak.

The speed of this expansion remains one of history's most astonishing transformations.

The Numbers Are Staggering

By 732 CE—exactly a century after Muhammad's death—Muslim armies had conquered:

The entire Persian Sassanid Empire
Two-thirds of the Byzantine Empire
All of North Africa
Most of the Iberian Peninsula (Spain and Portugal)
Territory stretching to the borders of India and China

This represented roughly half of the "known world" to medieval geographers. The Caliphate stretched 6,000 miles from the Atlantic Ocean to Central Asia.

How Did It Happen So Fast?

Several factors aligned perfectly. The two superpowers of the region—the Byzantine and Persian empires—had just exhausted themselves in decades of brutal warfare. Their treasuries were empty, their armies depleted, their populations weary.

The Arab armies, meanwhile, were unified by religious zeal and battle-hardened from desert warfare. They offered conquered peoples a simple deal: pay a tax and keep your religion, or convert and become equals. Many chose the latter.

Perhaps most importantly, many conquered peoples saw the Arabs as liberators. Byzantine religious persecution had alienated Christians in Egypt and Syria. Persian subjects resented heavy taxation. The new rulers often seemed preferable to the old.

The Battle That Finally Stopped Them

The expansion wasn't halted until 732 CE at the Battle of Tours in central France. Charles Martel's Frankish army defeated an Arab raiding force, marking the high-water point of Islamic expansion into Western Europe.

Some historians consider this one of the most decisive battles in world history. Others argue the Arab forces were merely raiders, not a serious invasion force, and would have retreated regardless.

Either way, the century of conquest was over. What followed was consolidation—and the creation of one of history's greatest civilizations.

The Legacy

This rapid expansion created a cultural zone stretching from Spain to Indonesia. Arabic became the language of science and philosophy. The preservation and translation of Greek texts in Baghdad would later spark Europe's Renaissance.

Trade routes flourished, connecting China to the Mediterranean. Mathematical innovations (including the numerals you're reading now) spread westward. Medical and astronomical knowledge advanced centuries ahead of Europe.

The political unity didn't last—the Caliphate fractured within centuries. But the religious and cultural unity endured. Today, 1.8 billion people follow the faith that conquered half the world in a single century.

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