  Coalition forming is investigated among countries, which are coupled with
short range interactions, under the influence of external fields produced by
the existence of global alliances. The model rests on the natural model of
coalition forming inspired from Statistical Physics, where instabilities are a
consequence of decentralized maximization of the individual benefits of actors
within their long horizon of rationality as the ability to envision a way
through intermediate loosing states, to a better configuration. The effects of
those external incentives on the interactions between countries and the
eventual stabilization of coalitions are studied. The results shed a new light
on the understanding of the complex phenomena of stabilization and
fragmentation in the coalition dynamics and on the possibility to design stable
coalitions. In addition to the formal implementation of the model, the
phenomena is illustrated through some historical cases of conflicts in Western
Europe.
