We introduce a simple growth model to investigate how the evolution of a society is influenced by international conflicts. We come to the result that in the long run three equilibria are possible; a war equilibrium, a peace equilibrium or cycles between war and peace. Which kind of equilibrium will be achieved depends on the effectiveness of weapons, the distribution of capital, intertemporal preferences and the production technology. In general, we conclude that the achievement of a long-lasting sustainable peace is possible, if we restrict the degree of economic inequality. The model delivers a normative reasoning for the foundation and the conservation of the European Union, even if redistribution of national incomes must take place to conserve it.