Samuel Phillips Huntington was an American political scientist who gained prominence through his "Clash of Civilizations"(1993, 1996) thesis of a new post-Cold War world order. Previously, his academic reputation had rested on his analysis of the relationship between the military and the civil government, his investigation of coups d'etat and for his more recent analysis of threats posed to the U.S. by contemporary immigration.
For those who cringe at Sam Huntington because of his "Clash of Civilizations" theory, give his earlier incarnation a chance. This book is brilliant. Civil-military relations, why the US defense bureaucracies work the way they do, Presidential prerogatives, service obligation and politics, it is all in there. I still think his dream of totally separate spheres for the military and civilian leadership is pie in the sky, but if you want a book that will stimulate your thinking about defense politics, look no further.