Islam took root throughout the East African coast in the 8th century, as part of a continual discourse between the inhabitants of the East Coast and traders from the Persian Gulf and Oman. After several decades, it became clear that Islam was able to attract more people than Christianity, which had been established by European missionaries.
In the 10th century, Arab merchants began to enter what is now Tanzania from Arabia and Mozambique from South Africa, bringing with them their religion. It eventually reached as far as Uganda, where it still remains the majority religion.
According to some sources, Islam may have even spread farther than this, reaching as far as Nigeria and Senegal through Arab slaves and traders. However, there are also sources that claim these regions are too remote and isolated to have ever experienced significant Muslim influence.
After initial resistance, most people on the East African coast embraced Islam. It was not until many years later that Christians started to emerge as a dominant force in the region.
Currently, Islam is the largest religion in Kenya (where it accounts for about 49 percent of the population), Ethiopia (30 percent), Tanzania (25 percent), and Somalia (20 percent).
Islam, like early Christianity, was monotheistic, meaning that Muslims worshiped just one God. They differed from Christians in that they believed that Jesus was only a prophet and not the son of God.
African slaves were important to early Islamic civilization and many scholars believe that knowledge about mathematics and science may have come to Africa through Arab slavery owners. The black skin of slaves made them valuable commodities in an era when white skin was considered superior. In fact, the term "black slave" is actually derived from Arabic words referring to dark-skinned people.
In addition to slaves, Arabs also transported large numbers of prisoners of war to areas where they could be used as labor or sold into slavery. These prisoners included blacks who had fought for other Africans states against Arab invaders.
Arab traders began visiting Africa's east coast as far back as the 7th century and by the 10th century they had established several settlements there. Known as "kafirs," or unbelievers in Islam, these traders taught the locals how to make boats out of wood and traded with them for ivory, gold, and salt.
Africa's East Islam arrived on the East African coast in multiple waves and at various eras. There is no specific date in the archives, although Islam is assumed to have spread by the 8th century. It is estimated that there were about 15 million Muslims in Africa by the start of the 14th century.
It is believed that the first immigrants to arrive in what would later become Tanzania were members of an Islamic army from Somalia. They landed in what is now known as Puntland in northern Somalia and fought with the local ruler against their common enemy, the Christian kingdoms to their south. After being defeated, they accepted defeat and adopted the new religion, forming a community that would later give birth to the Pulaar people.
Islam also arrived in Kenya through Puluwardis, a nomadic tribe who came from Persia (present-day Iran). In 739 AD, they invaded north-eastern Kenya, where they established a kingdom that would last until 1885. During this time, they integrated themselves into Kenyan society and taught the locals to read and write using the Quran. This aspect of Puluwardi history has been well documented thanks to some ancient coins that have been found near present-day Nairobi.
Islam expanded in this manner throughout and around the Sahara Desert. Furthermore, religion emerged in East Africa when Arab traders crossed the Red Sea and settled along the Swahili Coast in a second wave. The Arabs taught the locals how to make boats out of wood and traded with them for ivory and gold. In return, the Africans supplied the Arabs with slaves.
As you can see, Islam was brought to Africa by merchants who worked with the locals. There were no soldiers on these trading trips - the Muslims did not have enough money to pay for weapons. Instead, they bought peace with cash and trade.
In conclusion, Islam reached East Africa through peaceful means. No armies were used to conquer territory - only traders and teachers were sent to convert or educate the people.