I highly recommend a book not yet mentioned: Inside War: The Guerrilla Conflict in Missouri During the American Civil War, by Michael Fellman.

Published in 1989 by Oxford University Press, it is much more than a simple history of guerrilla fighting in Missouri. It is an in-depth analysis of the psycho-social interrelationships between the two sides in conflict and the civilian population caught in-between. The book, when read in the context of current ops, makes for quite interesting reading - especially the sections on Loyalty, Neutrality and Survival Lies and Collapse of the Sense of Security in the chapter on Civilians in Guerrilla War.

The book studies official attitudes of both sides, and compares them with the combatants' perception of self and others in the context of the conflict. There is much of value to be gained from this study in viewing today's war in Iraq. Cross-cultural perceptions between our forces and the various Iraqi players in the conflict are far more complex than those in 1860's Missouri during the Civil War - but I felt this book puts a valuable perspective on the combat effects of such views of the other side.