His long reign was a constant series of campaigns against the eastern tribes, the Babylonians, the nations of Mesopotamia and Syria, as well as Cilicia and Urartu. His armies penetrated to Lake Van and Tarsus, the Hittites of Carchemish were compelled to pay tribute, and Hamath and Damascus were subdued.

In 853 BC a league formed by the kingdoms of Hamath, Arvad, the Ammonites, "Ahab of Israel" and other neighboring kings, under the leadership of king Hadadezer of Damascus, fought an indecisive battle against him at Karkar (Qarqar), and other battles followed in 849 and 846 BC.

In 842 Hazael was compelled to take refuge within the walls of his capital. The territory of Damascus was devastated, and Jehu of Israel (whose ambassadors are represented on the Black Obelisk now in the British Museum) sent tribute along with the Phoenician cities. Babylonia had already been conquered as far as the marshes of the Chaldaeans in the south, and the Babylonian king put to death.

In 836 Shalmaneser made an expedition against the Tibareni (Tabal) which was followed by one against Cappadocia, and in 832 came the campaign in Cilicia. In the following year the old king found it needful to hand over the command of his armies to the Tartan (commander-in-chief), and six years later Nineveh and other cities revolted against him under his rebel son Assur-danin-pal. Civil war continued for two years; but the rebellion was at last crushed by Samas-Rimmon or Samsi-Hadad, another son of Shalmaneser. Shalmaneser died soon afterwards. He had built a palace at Calah, and the annals of his reign are engraved on an obelisk of black marble which he erected there.