Jamieson, Fausset and Brown on 2 Samuel 10:16

16. Hadarezer sent and brought out the Syrians that were beyond the river--This prince had enjoyed a breathing time after his defeat (2Sa 8:3). But alarmed at the increasing power and greatness of David, as well as being an ally of the Ammonites, he levied a vast army not only in Syria, but in Mesopotamia, to invade the Hebrew kingdom. Shobach, his general, in pursuance of this design, had marched his troops as far as Kelam, a border town of eastern Manasseh, when David, crossing the Jordan by forced marches, suddenly surprised, defeated, and dispersed them. As a result of this great and decisive victory, all the petty kingdoms of Syria submitted and became his tributaries (see on 1Ch 19:1).