In 2010 I wrote that economic issues are just another factor in decisions on war or peace. There is nothing to suggest that free trade leads to peace per se (The Liberal Divide over Trade, Peace, and War, International Relations, vol 24, number 2, June 2010).
This is not a particular popular viewpoint, certainly not among classical liberals and libertarians, for reasons written about before at this blog.
So it is nice to read in Dale C. Copeland’s new book Economic Interdependence and War (Princeton University Press 2015), that indeed it all depends upon the situation. Economic factors can just as easily be cause for war, as a cause for refraining from violence. Copeland does not write from the liberal tradition, but if he had, he could have used Adam Smith, David Hume or Friedrich Hayek in support for his argument.
Anyway, the good thing is that the free-trade -leads-to-peace thesis is slowly but surely being debunked. It makes for a better and more mature discussion about international relations, inside and outside liberalism.