The Iran nuclear deal brokered by Brazil and Turkey is an important moment, as the world becomes more multi-polar and less predictable.
Some people are reporting American chagrin that the Brazilians, in helping to strike the deal which will see some low-enriched uranium sent to Turkey in return for higher-grade nuclear fuel for a research reactor, may have stymied US-led attempts to achieve a similar but more comprehensive arrangement.
It's not so long since the US was regarded as "the hyper-power" and many still see it as the world's only superpower.
But as other nations - particularly Brazil, India, and China - grow stronger and more internationally assertive the result is likely to be more confusion in international politics.
It will also lead many smaller countries to indulge in power politics, playing big states off against one another.
Many around the world may have longed for an end to the era of American international dominance, but will they end up thinking they should have been more careful about what they wished for?
Are the Chinese any gentler in their extraction of minerals from Africa than US companies are? Does India offer better rights to workers as it hoovers up hi-tech jobs?
Or do Russian sales of weapons to Iran or Syria do any more to increase regional stability than US ones to Israel?
It might be argued, to extend market economics to the international sphere, that as the world becomes more multi-polar, power will be dispensed more efficiently.
But the counter-argument is that it will also become a less predictable place - witness the Brazil/Turkey deal with Iran - in which certain actors will behave with far less transparency or accountability than we are used to from the US.
A more multi-polar world could also be a less orderly one - particularly if the US, weighed down by its long campaigns in Iraq and Afghanistan, is more reluctant to intervene again.
In the mid-1990s Washington was cursed by many for non-intervention in Rwanda or the Balkans. After 9/11 it was denounced for intervening too freely.
Now, beset by economic woes and its long overseas wars, the trend is once again to be wary of foreign entanglements.
Nato's new Mission Statement released today, notes that were the alliance to disappear, "the prospects for international stability and peace would be far more uncertain than they are".
It also argues Nato aims to, "enhance international security, safeguard liberty, and promote the rule of law".
The alliance great and good that compiled the Mission Statement were wary about talking too explicitly about the dangers of a diminished US role in the world or of the "de-coupling" of European and American members of the Atlantic alliance in the future.
Perhaps then the most valuable role that Nato can play in the future is in managing the decline of the hyper-power, keeping it engaged in world events in a benign and more consensual way than it was under the Bush administration.
If the Brazil/Turkey deal with Iran shows us the greater potential for surprises in the future, then perhaps Nato can act as a comfort blanket in a new age of uncertainty.