Albert Barnes Commentary 2 Kings 8:28

"And he went with Joram the son of Ahab to war against Hazael king of Syria at Ramoth-gilead: and the Syrians wounded Joram." — 2 Kings 8:28 (ASV)

The goal of this war by the two kings against Hazael seems to have been the recovery of Ramoth-gilead, which Ahab and Jehoshaphat had unsuccessfully attempted fourteen years earlier (1 Kings 22:3–36). Joram probably thought that the rise of a new usurper to the throne presented a favorable opportunity to renew the war. It is also possible that Hazael was engaged at the time on his northern frontier, repelling one of the Assyrian attacks which, according to inscriptions, seem to have come against him in quick succession during his early years. In any case, the war appears to have been successful. Ramoth-gilead was recovered (2 Kings 9:14) and probably remained in the hands of the Israelites from that time on.

The Syrians wounded Joram – According to Josephus, Joram was struck by an arrow during the siege but remained until the city was captured. He then withdrew to Jezreel (1 Kings 18:45, 1 Kings 21:1), leaving his army under Jehu's command inside the city walls.