The Straight Path by John Esposito

But Abu Bakar controlled the Muslims with his wisdom. He ruled for two years and was succeeded by Omar. A man of rules, Omar played an important role in Muslim’s revival and also many areas were conquered in his era. His era shows great development within the Muslim world, not only as they conquered different parts of the Middle East and Africa, but also he solved many conflicts within the Muslim world. He established a few basic practices. He remained as a Caliph for almost a decade and during this time, Islam spread worldwide and he conquered large are of land as well. Hence, his era could be called the unforgettable era of Muslims. He established the first public treasury and also financial administration for the first time.
Umar succeeded by Usman, the third Muslim Caliph, ruled for almost twelve years. Islam spread worldwide during his era. He arranged the Koran in order and spread it all over with the same order. The Koran that is read by Muslim today is the same version. He was murdered by few young men, as anarchy among Muslims started at that time. He was succeeded by Ali, Shia Muslims consider him as their spiritual leader. Ali was famous for his bravery, his rule is still remembered as the one which kept Muslims united. But after all these Caliphs, Muslims never get united again.
After telling about the four Caliphs, the writer stated about Ummayad Caliphs. It was established in 661 and last for a century. Damascus was the capital of the Islamic World which got wider till that. It includes a great part of Asia and some part of Europe as well. Ummayad era is remembered as a golden era. Islamic conquests continued during this time, including Asia and Europe, the main parts conquered at that time were Central Asia, Spain, France and Indian subcontinent.