Verse 11. - And he said, etc. Thenius remarks, "We have here the briefest of warlike exhortations, but one most full of point and meaning." Joab recognized the full danger of their situation; for should he meet with any check in his attack on this vast host of mercenaries, he was well aware that the Ammonites, watching the battle with eager interest, would, on the first news of victory, rush upon Abishai with exulting fury; and the men with him, being only ordinary troops, would be disheartened by Joab's failure, so that without extraordinary bravery on their leader's part, they would give way, and all would be lost.
10:6-14 They that are at war with the Son of David, not only give the provocation, but begin the war. God has forces to send against those that set his wrath at defiance, Isa 5:19, which will convince them that none ever hardened his heart against God, and prospered. Christ's soldiers should strengthen one another's hands in their spiritual warfare. Let nothing be wanting in us, whatever the success be. When we make conscience of doing our duty, we may, with satisfaction, leave the event with God, assuredly hoping for his salvation in his own way and time.
then thou shall help me; detach a part of his army to his support and assistance:
but if the children of Ammon be too strong for thee, then I will come and help thee; in the same manner.