What does Judges 4:16 mean?

The Lord has given Barak and his men a decisive battle over Sisera and the Canaanite army (Judges 4:12–13). Apparently, sudden flooding of the Kishon River (Judges 5:21) and Deborah's well-timed command to attack (Judges 4:14) made Sisera's chariots ineffective and turned the battle dramatically in Israel's favor.

Sisera, seeing he would lose this battle, escaped to the northeast on foot (Judges 4:17). Whether this was cowardly, or sensible, is subject to different views. Most readers assume Sisera went entirely alone, but this seems unlikely. If he did go with any other soldiers, they are not mentioned. At the very least, Sisera is alone when he meets his fate, as decided in the following verses.

Any of Sisera's men not yet struck down by Barak's army attempted to flee back the way they had come, toward Harosheth-hagoyim to the west. Barak and his men chased down every one of them and killed them. Most battles, in most eras of history, rarely ended with more than a small percentage of the enemy dead. To defeat an enemy so thoroughly as to kill every soldier is a colossal event.