Albert Barnes Commentary 2 Samuel 8:9

"And when Toi king of Hamath heard that David had smitten all the host of Hadadezer," — 2 Samuel 8:9 (ASV)

Hamath - This appears as an independent kingdom as late as the time of Sennacherib (Isaiah 37:13). But in the time of Nebuchadnezzar, both Hamath and Arpad appear to have been incorporated into the kingdom of Damascus (Jeremiah 49:23).