Economics and the Civil War

The book Clash of Extremes: The Economic Origins of the Civil War, by Marc Egnal, who teaches in Toronto. His web site for this book is here.  My friends who appear to be economic determinists argue to me that economics cause wars, but I am skeptical.  I just don't think young men volunteer to go off for adventures based on patriotic feeling because it makes somebody rich.   The idea that most of the young men (now young women, too) sign up for the military based on national economic results does not correspond to what I have seen.  On the other hand, economics makes wars possible.  Economics may even induce governments to make belligerent decisions.  Governments obvious manipulate the circumstances.  However, I don't see the immediate link between economics and mass volunteering for war.  I guess I need to read this book.