Why? The answer is found in verse 14. There it tells us that the Lord fought for Israel and with God nothing is impossible. He created the sun and the moon, so why shouldn't He be able to make them stand still? What a day of victory! Once more God had proved Himself to be on their side, fighting for them.
As the bible says,"If God be for us, who can be against us?" If we have God on our side, we won't have to fear the enemy either. There may be times in the natural that it seems like we're losing, but we are on the winning side. God has everything under control.
What more can He do than what He has already done, to show His love for us? He gave His only Son to die for us, that we might be reconciled to Him. Surely He will help fight every enemy that comes our way.