1: (If these opponents are under the false impression that none can defeat a powerful and mighty force like theirs, you should tell them) "Have you not seen, with your own eyes how your Rabb dealt with the army which had elephants.
2: "You saw with your own eyes how He rendered their artful planning utterly unsuccessful.
3: (They had selected an unknown and unsuspected pass on the other side of the mountain, so that they could lead a sudden attack and take you unawares.) "But flocks of eagles and vultures (which normally fly over the armies to pick up remnants of dead bodies or other eatables) started hovering over their heads. In this way you realised from a distance, that some army was on the move behind the mountains (their secret plan was thus exposed).
4-5: "Therefore you climbed over the mountain and started pelting them with stones, crushing their army and making them to look like chewed-up stubble".
(All this happened before your very eyes. When such a mighty army can be defeated, then what about yourself. All your secret plans will also fail).