Charles Ellicott Commentary Jeremiah 46:2

"Of Egypt: concerning the army of Pharaoh-neco king of Egypt, which was by the river Euphrates in Carchemish, which Nebuchadrezzar king of Babylon smote in the fourth year of Jehoiakim the son of Josiah, king of Judah." — Jeremiah 46:2 (ASV)

Against Egypt, against the army of Pharaoh-necho. —This Egyptian king was the last of its great native sovereigns. He was the sixth king of the twenty-sixth dynasty of Manetho, succeeded his father Psammetichus in B.C. 610, and reigned for sixteen years. Herodotus (ii. 158, 159) relates that among his chief achievements was his endeavor to connect the Nile with the Red Sea, an enterprise that anticipated the Suez Canal. However, he was stopped by an oracle and then sent a fleet of Phoenician ships to circumnavigate Africa. One hundred and twenty thousand lives were reportedly sacrificed in the former enterprise. After abandoning this project, he turned his attention to other plans of conquest, defeated the Syrians at Magdolus, near Pelusium, and took Cadytis, a great city of Syria, which Herodotus describes as not much smaller than Sardis.

Some writers have identified this with the capture of Jerusalem in 2 Chronicles 36:3, considering the name Cadytis equivalent to Kadusha (meaning "the holy city"), thus anticipating the modern Arabic name El-Khuds. Herodotus, however (iii. 5), describes it as near the coast, and this has led to its identification with Gaza, Kedesh-Naphtali, or a Hittite city—Ketesh—on the Orontes, near where the great commercial and military road turned off towards Damascus and the Euphrates. In any case, it was during this invasion, directed against the Babylonian Empire then ruled by Nabopolassar (Nebuchadnezzar's father), that Necho defeated and slew Josiah at Megiddo (2 Chronicles 35:20–24), deposed Jehoahaz, and appointed Jehoiakim (2 Chronicles 36:4).

Accordingly, some writers (R. S. Poole, in Smith’s Dict. Bible, Art. Pharaoh-necho) identify Megiddo with the Magdolus of Herodotus. Necho's army advanced and took the city of Carchemish, which some (Hitzig) identify with Circesium, an island formed by the confluence of the Chaboras and the Euphrates, while others (Rawlinson) identify it with a Hittite city, now Jerablus (a corruption of the Greek Hierapolis), much higher up the Euphrates. (See Note on Isaiah 10:9). After this capture, Necho appears to have returned to Egypt. Three years later (B.C. 606), Carchemish was retaken by Nebuchadnezzar, resulting in the almost total defeat of Necho’s army, as Necho himself had already returned to Egypt. It is this defeat that Jeremiah now describes, as if in a song of anticipated triumph over the downfall of the Egyptian oppressor.