Jer 46:1-2
This is what occurred as the word of Jehovah to Jeremiah the prophet concerning the nations: 2 For Egypt, concerning the military force of Pharaoh Necho the king of Egypt, who happened to be by the river Euphrates at Carchemish, whom Nebuchadrezzar the king of Babylon defeated in the fourth year of Jehoiakim the son of Josiah, the king of Judah
Key points
The Battle of Carchemish takes place.
This is the 4th year of Jehoiakim and the 1st year of Nebuchadnezzar. It is when Pharoah Necho loses power over Jehoiakim and Jehoiakim becomes a vassal to Nebuchadnezzar. For the first three years after the Battle of Carchemish, Jehoiakim is subject to Nebuchadnezzar, then after three years, Jehoiakim rebels against Nebuchadnezzar.