The Axums were an offshoot of the Kingdom of Sheba. The Kingdom of Sheba controlled access to the Red Sea, thereby becoming rich through taxation of all commerce that entered the waterway. Sheba established the colony of Axum. When Sheba declined, Axum became independent. Axum developed into a major trading center in its own right, serving as a major exporter of ivory, frankincense, and slaves. In the 4th century, the Axums -- who were competing with Kush -- invaded the Kingdom and captured it. It was also at this time that the Axumite kingdom converted en masse to Christianity. The Axums' form of Christianity, which originated in Egypt, became known as the Coptic Church.
With the growth and expansion of Islam, Axum inevitably declined. Trade routes began to bypass Axum. The capital was moved further into the mountains and Axum became known as an hermetic region. By the 8th century, Axum came into conflict with a number of Muslim coastal states. For a period of time, Axum was able to force these states to pay tribute and becoming -- once again -- a prime trading force in the area.
In the 12th century, the Zagwe dynasty assumed control of the country now known as Ethiopia. The Zagwes centralized the government and extended Christian missionary efforts.