Albert Barnes Commentary 2 Chronicles 14:12

"So Jehovah smote the Ethiopians before Asa, and before Judah; and the Ethiopians fled." — 2 Chronicles 14:12 (ASV)

The defeat of Zerah is one of the most remarkable events in the history of the Jews. On no other occasion did they meet in the field and overcome the forces of either of the two great monarchies between which they were placed. It was seldom that they ventured to resist unless from behind walls; rulers like Shishak, Sennacherib, Esarhaddon, and Nebuchadnezzar were either unopposed or only opposed in this way. On the one other occasion when they took the field—under Josiah against Necho—their boldness resulted in a most disastrous defeat (2 Chronicles 35:20–24). Under Asa, however, they appear to have gained a complete victory over Egypt.

The results that followed were most striking. The southern power could not rally from the blow and, for over three centuries, made no further effort in this direction. As Assyria grew in strength, it finally penetrated to Egypt itself under Sargon and Sennacherib. Consequently, all fear of Egypt as an aggressive power ceased, and the Israelites learned instead to lean on the Pharaohs for support (2 Kings 17:4; 2 Kings 18:21; Isaiah 30:2–4; and elsewhere). Friendly ties alone connected the two countries, and it was not until 609 B.C. that an Egyptian force again entered Palestine with hostile intent.