After the death of Muhammad, there was a split between Muslims as to how to choose the successor of Islam, called a caliph. Sunni Muslims believe that the people should elect the strongest successor, while the Shi'a believe that only Allah should chose the next caliph. Mu'awiyah became the sixth caliph, and he established the Umayyad Dynasty. The Umayyads created a Muslim empire which grew rapidly, spreading across North Africa and into Spain, where Islamic armies conquered the Visigoths. The capital city of the Umayyad Caliphate in Spain was Cordoba. The Pillars of Hercules was renamed the Rock of Gibraltar (Spanish for Mountain of Tariq), in honor of the Muslim general, Tariq, who lead the attack. When a caliph called for a jihad, it was a loyal follower's duty to respond. The Muslims in Spain were called the Moors, they crossed over the Pyrenees Mountains into France, threatening the Frankish Empire of theMerovingians. In the East, the Byzantine empire was under attack. The Romans lost a large part of their empire to the Islamic armies, but Greek Fire would save Constantinople from the fleets of Muslim ships.
Advances of the Islamic World
The Christian West and East looked at Muslims armies as raiding barbarians, but that was far from the truth. The Muslims inherited the math, science, medicine, and architecture of the Hellenistic world. From captured Chinese prisoners-of-war, the Muslims learned the art of paper making. This made books cheap and plentiful in the Muslim world. Reading and writing increased, along with learning. Baghdad, one of the capitals of the Islamic world, had a library called the "House of Wisdom." Muslim doctors understood the need to quarantine sick patients, so disease would not spread to other people. They were one of the first groups to understand that a healthy diet helped patients to recover from illness. The Arabic world understood the concept of zero, while the Romans had no zero in their awkward number system; we still us Arabic numbers today. Perhaps copying an earlier Hellenistic model, the Muslims created the astrolabe, a type of computer that charted the movements of the planets, moon, sun, and stars. The astrolabe helped sailors to stay on course when they were out to sea.