It is a key fact about American policy in Vietnam that the withdrawel of American troops was built into it from the start. None of the presidents who waged war in Vietnam contemplated an open-ended campaign; all promised the public that American troops would be able to leave in the not-too-remote future. The promise of withdrawel precluded a policy of occupation of the traditional colonial sort, in which a great power simply imposes its will on a small one indefinitely.