  I study the relationship between the likelihood of a violent domestic
conflict and the risk that such a conflict "externalizes" (i.e. spreads to
another country by creating an international dispute). I consider a situation
in which a domestic conflict between a government and a rebel group has the
potential to externalize. I show that the risk of externalization increases the
likelihood of a peaceful outcome, but only if the government is sufficiently
powerful relative to the rebels, the risk of externalization is sufficiently
high, and the foreign actor who can intervene in the domestic conflict is
sufficiently uninterested in material costs and benefits. I show how this model
helps to understand the recent and successful peace process between the
Colombian government and the country's most powerful rebel group, the
Revolutionary Armed Forces of Colombia (FARC).
