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Islam spread through military conquest, trade, pilgrimage, and missionaries.
Arab Muslim forces conquered vast territories and built imperial structures over time.
Most of the significant expansion occurred during the reign of the Rashidun from 632 to 661 CE, which was the reign of the first four successors of Muhammad.
The caliphate—a new Islamic political structure—evolved and became more sophisticated during the Umayyad and Abbasid caliphates.
Over a period of a few hundred years, Islam spread from its place of origin in the Arabian Peninsula all the way to modern Spain in the west and northern India in the east.
Islam traveled through these regions in many ways. Sometimes it was carried in great caravans or sea vessels traversing vast trade networks on land and sea, and other times it was transferred through military conquest and the work of missionaries. As Islamic ideas and cultures came into contact with new societies, they were expressed in unique ways and ultimately took on diverse forms.
To begin to understand the rich history of Islam, let’s start with the historical context and events that led to Islam’s spread. For example, Islam initially spread through the military conquests of Arab Muslims, which happened over a very short period of time soon after the beginning of Islam. However, only a small fraction of the people who came under Arab Muslim control immediately adopted Islam. It wasn’t until centuries later, at the end of the eleventh century, that Muslims made up the majority of subjects of the Islamic empires.
The spread of Islam through merchants, missionaries, and pilgrims was very different in nature. These kinds of exchanges affected native populations slowly and led to more conversion to Islam. As Islamic ideas traveled along various trade and pilgrimage routes, they mingled with local cultures and transformed into new versions and interpretations of the religion.
Another important thing to note is that not all military expansion was Arab and Muslim. Early on in Islamic history, under the Rashidun caliphate—the reign of the first four caliphs, or successors, from 632 to 661 CE—and the Umayyad caliphate, Arab Muslim forces expanded quickly. With the Abbasids, more non-Arabs and non-Muslims were involved in the government administration. Later on, as the Abbasid caliphate declined, there were many fragmented political entities, some of which were led by non-Arab Muslims. These entities continued to evolve in their own ways, adopting and putting forth different interpretations of Islam as they sought to consolidate their power in different regions.
The first Arab Muslim empire
During the seventh century, after subduing rebellions in the Arabian peninsula, Arab Muslim armies began to swiftly conquer territory in the neighboring Byzantine and Sasanian empires and beyond. Within roughly two decades, they created a massive Arab Muslim empire spanning three continents. The Arab Muslim rulers were not purely motivated by religion, nor was their success attributed to the power of Islam alone, though religion certainly played a part.
Buddhism was almost banished from the territories occupied by Arab rulers. Although there was a perceived decline prior to the Muslim invasion, this event ended up cleansing the practice with the destructions of monastic universities (places where Buddhism was taught).
Regarding Hinduism, it is considered that the expansion of the Arab empire in northern India was one of the bloodiest episodes in history. The Mughal Emperor, Akbar, was tolerant towards Hindu practice in these conquested territories. However, his successor Aurangzeb was heavily reluctant to tolerate this practice. Hindus were ultimately given the "religious minority" status.
Islam considers Jesus, Abraham, and Moses as prophets as Muslim prophets. However, the texts wrote by them in the Gospels and Torah was corrupted by the Jewish and Christian religion.
Different religions was well treated by rulers of the Arab empire.
All the rulers of Arab empire were Muslims so they allow the people of different religions to follow their own religion because the holy book Quran forbid the Muslim rulers to force conversion of non-Muslims to Islam. These Arab rulers only impose low taxes on the people of other religion and in return the Muslims ruler provide security to their property and family.