Political Scientist Samuel P. Huntington

Henry Rosovsky, a longtime friend and a former Harvard dean, described Dr. Huntington as "clearly one of the most influential political scientists of the last 50 years."

Rosovsky said in a statement released by Harvard: "Every one of his books had an impact. These have all become part of our vocabulary."

His first book, "The Soldier and the State: The Theory and Politics of Civil-Military Relations," published in 1957, was prompted, at least in part, by President Harry S. Truman's firing of Gen. Douglas MacArthur during the Korean War. The young scholar, not yet 30 when the book was published, argued that America's liberal society required the protection of a conservative military establishment that recognized the "irrationality, weakness and evil in human nature."

"The Soldier and the State" aroused passions, and Harvard's Department of Government denied Dr. Huntington tenure the next year. He and a close friend, Zbigniew Brzezinski, also denied tenure, decamped to Columbia University. Four years later, Harvard invited both men back as tenured professors. Dr. Huntington accepted; Brzezinski stayed at Columbia.

In 1964, Dr. Huntington co-authored, with Brzezinski, "Political Power: USA/USSR," a major study of international relationships in the Cold War.

"Political Order in Changing Societies" (1969) "challenged the orthodoxies of the 1960s in the field of development," said Jorge Dominguez, vice provost for international affairs at Harvard. "Huntington showed that the lack of political order and authority were among the most serious debilities the world over. The degree of order, rather than the form of the political regime, mattered most."

Dr. Huntington's last book, published in 2004, was "Who Are We? The Challenges to America's National Identity." He expressed concern that because Hispanic immigration was so large, the nation could not adequately assimilate Spanish-speaking newcomers. His argument was, as usual, controversial.

Samuel Phillips Huntington was born in New York to a father who was a publisher and a mother who was a writer. He graduated from Yale in 1946 at 18. After serving in the Army at Fort Eustis in Virginia for a year, he received a master's degree in 1948 from the University of Chicago and a doctorate in 1951 from Harvard.

He served for two years as a National Security Council official under President Jimmy Carter. He also co-founded the influential journal Foreign Policy (now published by The Washington Post Co.) and headed the Olin Institute for Strategic Studies at Harvard.

Survivors include his wife of 51 years, of Martha's Vineyard; two sons, Nicholas Phillips Huntington of Newton, Mass., and Timothy Mayo Huntington of Boston; and four grandchildren.