Complex sentence: In November 633, the Persian counter-attack was repulsed by Khalid and in December 633, Muslim forces reached the border city of Firaz, where Khalid defeated the combined forces of the Sassanid Persians, Byzantine Romans and Christian Arabs in the Battle of Firaz.
Split into simpler sentences: In November 633, the Persian counter-attack was repulsed by Khalid. In December 633, Muslim forces reached the border city of Firaz, where Khalid defeated the combined Sassanid, Byzantine, and Christian Arab armies in the Battle of Firaz.