“into a panic.” This is what Yahweh did to the Egyptians; the Hebrew uses the same word for panic (Exod. 14:24-25).
“army.” Same word as in Exod. 14:24 with the Egyptian army.
“the mouth of the sword.” Used to show great destruction, as if the sword was eating its victims (see commentary on Josh. 6:21).
“got down from.” The chariots were supposed to give the Canaanites an advantage, but with God’s intervention, they became a liability.