It's astounding the degree to which these communities are intermarried. Iraq is a crazy quilt of ethnicities and religious sects.
What is certain about the future is that even the best efforts to predict the conditions of future war will prove erroneous. What is important, however, is to not be so far off the mark that visions of the future run counter to the very nature of war and render American forces unable to adapt to unforeseen challenges.
Because war is a competition involving life and death, and in which national security and vital interests are at stake, establishing an objective other than winning is not only counterproductive, but also irresponsible and wasteful. In some circumstances, it is also unethical.
It is important to understand how leaders have adapted and thought about war and warfare across their careers. 'The Autobiography of General Ulysses S. Grant: Memoirs of the Civil War' is perhaps the best war memoir ever written.
My personal experience in Ninawa Province has been that, at the most fundamental level, people don't really care if it's a Shiite, a Sunni, a Kurd, or a Turkoman that's providing them security as long as that force treats them with respect.
What we can afford least is to define the problem of future war as we would like it to be and, by doing so, introduce into our defense vulnerabilities based on self-delusion.