What was the first major empire in the world to officially adopt Christianity as a state religion?
Kingdom of Aksum (Africa)
In about 316 AD, Frumentius and his brother Edesius from Tyre were taken to the Ethiopian court as slaves. They were given positions of trust by the monarch, and converted members of the royal court to Christianity. Ethiopia, a major empire at the time, was the second country to officially adopt Christianity (after Armenia).