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.