In verse 3 we read: "And all the nations that fight against Zion, and that distress her, shall be as a dream of a night vision; yea, it shall be unto them, even as unto a hungry man which dreameth, and behold he eateth but he awaketh and his soul is empty; or like unto a thirsty man which dreameth, and behold he drinketh but he awaketh and behold he is faint, and his soul hath appetite; yea, even so shall the multitude of all the nations be that fight against Mount Zion."
There isn't much substance to the enemies of God after all. They are more like a phantom than a real threat. When the moment comes to remove them, their departure will be so abrupt, complete and liberating, they will seem in hindsight to have never been there at all. The survivors will be asking themselves: "What, exactly, was it about them that made them seem threatening?" In the wake of their complete defeat, they will seem impotent. Fighting against God always leaves mankind looking foolish and weak. It will be like looking on the surface of a calm Red Sea after it drowned an Egyptian army and asking: "What was it about Pharaoh that worried us?"