Carchemish

fortress of Chemosh, a city on the west bank of the Euphrates (Jer 46:2; 2Chr 35:20), not, as was once supposed, the Circesium at the confluence of the Chebar and the Euphrates, but a city considerably higher up the river, and commanding the ordinary passage of the Euphrates; probably identical with Hierapolis. It was the capital of the kingdom of the northern Hittites. The Babylonian army, under Nebuchadnezzar, the son of Nabopolassar, here met and conquered the army of Pharaoh-necho, king of Egypt (B.C. 607). It is mentioned in monuments in B.C. 1600 and down to B.C. 717.

EBD - Easton's Bible Dictionary