My annual Theory Camp is reading Tocqueville's Democracy in America.
Tocqueville says that aristocratic societies glorify war and disparage greed. Democratic societies disparage war, but glorify ambition. The danger for democratic societies is that their armies do seek, if not glorify, war. Armies in democratic societies are prone to coups if not given an external enemy to fight.
In the United States we have a very professional military, not at all likely to stage a coup due to inaction. This is due, in part, to the fact that they are frequently engaged in wars - we have two and a half going at the moment. When we do have peace, our military is not likely to agitate for war.
So if business in a democracy is against war because it is bad for business, and our military is not eager for war since they get tested enough, in what structural location in our society would we expect to find promoters of war? Military contractors. And if military contractors should become disproportionately influential in any particular party or administration - perhaps through a revolving door that put, say, a defense secretary in charge of a large military contractor, and then back into government as de facto head of warmaking - we might expect that kind of government to start more voluntary wars.