There's actually a pretty decent theory that war causes an economic boom and in the long run can produce more healthy economies. A good example is World War 2 America. But almost everyone knows that part of the theory. What isn't discussed is the other side of said theory. The lack of war can make for terrible economies and corrupt governments. Looking at Sub Saharan Africa, this is a prime example. Since interstate war is so rare there, the militaries are not at the level they should be to contain the intrastate conflicts ravaging their states. As such, this paves the way for low economic development, high unemployment, high crime rates and a high level of corruption. Thus, one can make a good argument that war (and the preparing for war aspect of statemaking) can and has led to better economies and better state of governing. This isn't to say that always happens nor am I saying that more war should happen, mind you.