Carchemish appears once, in Nephi1’s quotation of Isaiah1, where it heads a list of cities the Assyrian king names to boast that his conquests are interchangeable: “Is not Calno as Carchemish? Is not Hamath as Arpad? Is not Samaria as Damascus?” (2 Nephi 20:9). In the passage the king uses these already-fallen cities as a benchmark, threatening to do to Jerusalem and Samaria what he had done to them.
Historically, Carchemish stood in northern Syria on the Euphrates River and was taken by Assyria during its westward expansion. It was later the site of the battle around 605 B.C. in which Nebuchadnezzar of Babylon defeated Pharaoh Necho of Egypt by the Euphrates, in the fourth year of Jehoiakim of Judah (Jeremiah 46:2).