What Does Exodus 14:7 Mean?

And he took six hundred chosen chariots and all the other chariots of Egypt with officers over all of them. The "six hundred chosen chariots and all the other chariots of Egypt" is Egypt's full chariot force deployment: the six hundred chosen (Hebrew: bachur, picked/elite) chariots are the premier chariot units, with the rest of Egypt's chariot forces supplementing. The "all the other chariots" indicates this is Egypt's total chariot mobilization, not a detachment. Egypt committed its maximum chariot force to the Israel pursuit: the largest possible military deployment against an unarmed (by Egyptian military standards) slave population.

The "officers over all of them" (Hebrew: shalishim, third-men, the experienced chariot officers who rode as the third crew-member in the chariot) indicates full professional military staffing: not a rushed conscript force but Egypt's professional chariot corps at full operational readiness. The military detail in verse 7 is the narrator's way of establishing the maximum possible human military threat against which YHWH's sea-crossing miracle will be measured. The more powerful the pursuing army, the more complete YHWH's victory over it at the sea.

Six hundred is a number that carries structural significance in Exodus (six hundred thousand men departed Egypt in Exodus 12:37): Pharaoh deploys six hundred elite chariots against the six-hundred-thousand who left. The numerical juxtaposition is suggestive: Egypt's six hundred best chariots against Israel's six hundred thousand. The ratio (roughly 1 chariot per 1000 Israelites) shows the scale of the military asymmetry, but the asymmetry is resolved by YHWH at the sea in Israel's favor, not Egypt's.