Samuel Huntington, a political scientist best known for his views on the clash of civilizations, has died, Harvard University announced Saturday. He was 81.

Huntington had retired from active teaching in 2007 after 58 years at Harvard. He died Wednesday on Martha's Vineyard, an island south of Cape Cod, Mass. His research and teaching focused on American government, democratization, military politics, strategy, and civil-military relations.

He argued that in a post-Cold War world, violent conflict would come not from ideological friction between countries, but from cultural and religious differences among the world's major civilizations.

He identified those civilizations as western (including the United States and Europe), Latin American, Islamic, African, Orthodox (with Russia as a core state), and Hindu, Japanese, and "Sinic" (including China, Korea, and Vietnam).

Huntington made the argument in a 1993 article in the journal Foreign Affairs, then expanded the thesis into a book, The Clash of Civilizations and the Remaking of World Order, which was published in 1996. The book has been translated into 39 languages.

In all, Huntington wrote 17 books including The Soldier and the State: The Theory and Politics of Civil-Military Relations, published in 1957 and inspired by President Harry Truman's firing of Gen. Douglas MacArthur, and Political Power: USA-USSR, a study of Cold War dynamics, which he co-authored in 1964 with Zbigniew Brzezinski.

His 1969 book, Political Order in Changing Societies, analyzed political and economic development in the Third World.

"Sam was the kind of scholar that made Harvard a great university," Huntington's friend of nearly six decades, economist Henry Rosovsky said in a statement released by the university.

Huntington was born on April 18, 1927, in New York City. He received his bachelor of arts degree from Yale in 1946, served in the U.S. army, earned a master's degree from the University of Chicago in 1948, and a doctorate from Harvard in 1951.