In coming years, as historians reflect upon what was achieved at this week's United Nations summit in New York, one decision may stand out.
If all goes as planned, the world will vow today "to take collective action, in a timely and decisive manner should peaceful means be inadequate and national authorities manifestly fail to protect their populations from genocide, war crimes, ethnic cleansing and crimes against humanity".
This promise, part of a new doctrine called the responsibility to protect, reflects a profound shift in international law, whereby a growing sense of global responsibility for atrocities is increasingly encroaching upon the formerly sanctified concept of state sovereignty.
While possibly never more than a convenient fiction, sovereignty has been the rock of international relations for 350 years, and the guiding framework around which the United Nations is organised. It remains deeply important to most UN member states.
That means that any efforts to interfere in domestic affairs have traditionally been given short shrift, and continue to face strong opposition from countries such as China and Russia. But massacres in Rwanda, Bosnia and most recently the killings in the Sudanese region of Darfur have created a growing sense that sovereignty should no longer remain inviolable when the worst abuses take place.
Kofi Annan, the UN secretary-general, gave a stark message to theb summiteers. "Excellencies," he said, "you will be pledged to act if another Rwanda looms." Paul Kagame, the Rwandan president whose rebel army eventually halted the 1994 genocide in Rwanda after the international community stood by, issued a similar appeal:
"Never again should the international community's resolve to tackle these crimes be found wanting. Let us be sure preventive interventions are the rule rather than the exception."
Aid groups such as Oxfam International say the UN declaration, the latest manifestation of an emerging principle of the "the right to protect" is the most important result of the summit.
That is not to say instant results are expected. Even the most ardent supporters of the responsibility to protect - an idea that emerged in the 90s - are under no illusions it will start saving lives immediately.
A study of recent atrocities, from Rwanda to the Balkans to Sudan, demonstrates how each situation was subject to the vagaries of great power relations.
Permanent members of the UN Security Council made it clear their national interests remained paramount. They strongly resisted demands by India that they suspend their veto over "responsibility to protect" decisions; and the US asserts that R2P, as it is sometimes known, amounts to moral pressure rather than legal obligation.
Robert Mugabe, the Zimbabwean president, also voiced the deep suspicions shared by many that the principle could be used as a cynical ploy to pursue an aggressive foreign policy, an argument bolstered by the US invasion of Iraq.
"Concepts such as humanitarian intervention and the responsibility to protect need careful scrutiny in order to test the motives of their proponents," he said.
Although the summit language fell short of the original scope of advocates who sought the right to apply the principle to a more general case of 'widespread killing'. Simon Chesterman, an international legal expert at New York University, says its adoption was remarkable.
"It's a lot more than I would have expected a couple of years back," he said. "What's really important is that previously (each) action (in response to atrocities) has been justified as unique, exceptional, one of a kind...What we're seeing is a progressive redefinition of sovereignty in a way that would have been outrageous 60 years ago."