The Clash of Civilizations is a theory that people's cultural and religious identities will be the primary source of conflict in the post-Cold War world. It was proposed by political scientist Samuel P. Huntington in a 1992 lecture at the American Enterprise Institute, which was then developed in a 1993 Foreign Affairs article titled “The Clash of Civilizations?” in response to his former student Francis Fukuyama's 1992 book, The End of History and the Last Man. Huntington later expanded his thesis in a 1996 book The Clash of Civilizations and the Remaking of World Order.
The phrase itself was earlier used by Bernard Lewis in an article in the September 1990 issue of The Atlantic Monthly titled “The Roots of Muslim Rage”. Even earlier, the phrase appears in a 1926 book regarding the Middle East by Basil Mathews: Young Islam on Trek: A Study in the Clash of Civilizations.