Rezin was king of Syria. Damascus was Syria’s capital city.
Pekah was the king of Israel from 740 to 732 BC. He was a famous warrior (2 Chronicles 28:5–8).
Pekah and Rezin began to attack Jerusalem while Jotham was king, from 750 to 732 BC. They increased their attacks during the early years of young King Ahaz (2 Kings 15:37; 16:5).