The signing of a new strategic arms limitation treaty on Thursday is a success for President Barack Obama.
But the interesting thing is how the US is the only power that really feels confident about cutting nuclear weapons, and how that holds back wider progress towards disarmament, non-proliferation, and even, that goal beloved of visionary speech makers, the nuclear free world.
Under the agreement to be signed in Prague today, the US and Russia will each cap their strategic nuclear arsenals at 1,550 warheads.
This new limit in fact simply codifies the shrinking of these forces that has taken place since the last round of superpower arms reductions.
The White House would have been happy for deeper cuts, but the Russians were not.
Russia also maintains substantial stockpiles of so-called tactical nuclear weapons such as artillery shells and air dropped bombs that are not included in the new limits, as well as large amounts of chemical weapons.
Why do they do so when their conventional forces have shrunk to a tiny fraction of their Cold War total?
The answer is simple enough - nuclear weapons are one of the few vestiges of the former Soviet superpower that give the Kremlin an air of international importance.
If that seems contemptible, consider Britain's actions in the light of another of Mr Obama's initiatives, the Nuclear Policy Review announced at the start of this week.
America has just renounced the possible use of nuclear weapons against non-nuclear states that are compliant with the Non Proliferation Treaty.
This removes some of the ambiguity which the Pentagon insisted for decades was essential for nuclear deterrence.
For that reason it is an important move, even if some of the obvious US potential targets such as North Korea or Iran have been explicitly ruled out of the new pledge.
Wouldn't Britain, with its pocket sized nuclear forces, do well to follow suit?
No, according to people I've been speaking to in government. Attempts by Prime Minister Gordon Brown to follow the US Nuclear Policy Review, have been blocked by the Ministry of Defence (MoD), say insiders.
Britain apparently wishes to maintain the "ambiguity" of a posture that includes a possible nuclear strike against Syria or indeed Bolivia, just to pluck some random examples out of the air.
As Britain struggles to finance the replacement of its single remaining nuclear system, Trident, it finds it hard to rule out such bizarre possibilities.
Britain, then is not so different from Russia in wishing to retain the status of a nuclear weapon state, it just uses slightly different arguments, for example about the unpredictability of the modern world.
Whitehall enthusiasts for a British version of the US Nuclear Policy Review had hoped that it might add some small weight to Mr Obama's attempts to halt the proliferation of nuclear weapons more generally.
The MoD's obstruction, apparently added another reason for Mr Brown not to attend next week's nuclear disarmament conference in Washington.
At that conference, Mr Obama will try to use the new treaty with Russia or policy review to strengthen his hand in preventing the proliferation of weapons - Iran is an obvious target of such diplomacy.
But the conference is likely simply to underline a salient truth: that only the US feels big and safe enough to conduct this kind of diplomacy with any real sincerity.
Countries like Pakistan, for reasons best known to themselves, are increasing their nuclear stockpiles despite the threat to the security of those weapons.
Israel remains outside any meaningful supervision in this area.
Iran continues to play its decade-long game of obfuscation with the international community, feeding the impression that it is racing to complete its own atomic arsenal.
While the US tires of the burden and risks of being a nuclear superpower, everyone else it seems wants to buttress their claims to regional or global influence.