Anyone who has ever studied the history of American diplomacy, especially military diplomacy, knows that you might start in a war with certain things on your mind as a purpose of what you are doing, but in the end, you found yourself fighting for entirely different things that you had never thought of before. In other words, war has a momentum of its own and it carries you away from all thoughtful intentions when you get into it.
-George F. Kennan
Quoted by Mark Danner, Iraq: The War of the Imagination New York Review of Books
via Mark Shea