This sufficiently indicates the greatness of the danger to Israel from this formidable league of Ammonites and Syrians.

All the host of the mighty - All his worthies, and the flower of his army.

And when David heard of it,.... Of the preparation made by the Ammonites to fight with him:
he sent Joab and all the host of the mighty men: he sent out Joab his general, and an army under his command, consisting of men of strength, valour, and courage; or all the host and the mighty men, as Kimchi and Ben Melech, the famous mighty men mentioned in 2-Samuel 23:8; he did not think it advisable to wait for the Ammonites, but carried the war into their own country, and, instead of suffering them to invade his dominions, he invaded theirs.

When David heard of these preparations and the advance of the Syrians into the land, he sent Joab and his brave army against the foe. הגּבּורים (the mighty men) is in apposition to כּל־הצּבא (all the host): the whole army, namely the heroes or mighty men, i.e., the brave troops that were well used to war. It is quite arbitrary on the part of Thenius to supply vav before הגּבּורים; for, as Bertheau has observed, as never find a distinction drawn between the gibborim and the whole army.