This work presents a basis for a better understanding of the foreign policies of Muslim states and Muslim in non-Muslim states with special reference to the Muslims in Mindanao. The study reveals that, after centuries of struggle and war, the Muslims and Christians have finally accepted the principle of co-existence and adjusted their once rigid and inflexible doctrines to international relations. It is suggested that a re-examination of the International Law on War be made taking into consideration not only the Christian and western views but also the Eastern and Islamic legal-theories of war.