Adam Clarke on Jeremiah 46:2

Pharaoh-necho - This was the person who defeated the army of Josiah, in which engagement Josiah received a mortal wound, of which he died, greatly regretted, soon after at Megiddo. After this victory, he defeated the Babylonians, and took Carchemish; and, having fortified it, returned to his own country. Nabopolassar sent his son Nebuchadnezzar with an army against him, defeated him with immense slaughter near the river Euphrates, retook Carchemish, and subdued all the revolted provinces, according to the following prophecies.