Complex sentence: Makuria was one of the few states in the world to repulse Muslim invasions led by the Rashidun Caliphate when they defeated an Arab army at the First Battle of Dongola in 642.
Split into simpler sentences: Makuria was one of the few states in the world to resist effectively Muslim conquests led by the Rashidun Caliphate. They defeated an Arab army at the First Battle of Dongola in 642.