Morality in Foreign Policy
Our notions of morality are based on interpersonal relations, but how well do the scale into relations of nations? For much (or all) of human history the answer has been hardly at all. There is one standard for the in group, be it clan, tribe, nation or religion, and another for the out group. Occasional attempts to introduce moral standards into the relations between nations took a concrete (if unsuccessful) step in the Twentieth Century with the creation of the League of Nations, and later with the United Nations.
The animating principle behind such ideas has not been that nations would not pursue their own interests, as people has always done, but that there would be some minimum standards, much as human societies have attempted to impose(mostly successfully) on their members from time immemorial (or at least 50,000 years or so). To call these efforts a success would be a great exaggeration but the considerations have at least come up.
The issues of colonialism and genocide have been central. Morality was hardly the principal force in the disruption of the old colonial empires, but it was a force, and a substantial one. Countless genocides have marked human history, but the Nazi genocide against Jews and some others marked sort of a milestone: the victims were among the most accomplished and literate people of Europe. Conventions against genocide were adopted, and some attempts were made to enforce them.
Genocide itself has hardly gone out of fashion. Cambodians, Rwandan Tutsis, Kurds, and at least half a dozen others have been victims since WW II. One reason that Obama intervened in Iraq was the genocidal actions of ISIL against Yasidis, and potentially Kurds. So when exactly is a Superpower - the Superpower - justified in intervening in a civil war? That's a conundrum.