What does 2 Chronicles 14:9 mean?

He built fortified cities in Judah; for the land was quiet, and he had no war in those years, because Yahweh had given him rest.

For he said to Judah, “Let us build these cities, and make walls around them, with towers, gates, and bars. The land is yet before us, because we have sought Yahweh our God. We have sought him, and he has given us rest on every side.” So they built and prospered.

Asa had an army of three hundred thousand out of Judah who bore bucklers and spears, and two hundred eighty thousand out of Benjamin who bore shields and drew bows. All these were mighty men of valor.

Then Asa went out to meet him, and they set the battle in array in the valley of Zephathah at Mareshah.

Asa cried to Yahweh his God, and said, “Yahweh, there is no one besides you to help, between the mighty and him who has no strength. Help us, Yahweh our God; for we rely on you, and in your name are we come against this multitude. Yahweh, you are our God. Don’t let man prevail against you.”

So Yahweh struck the Ethiopians before Asa and before Judah; and the Ethiopians fled.