Logic v politics

But Mr Obama has followed this logic several steps further. He did not,as some inside and outside his administration wanted,declare that America would never be the first to use its nuclear weapons. That would have unsettled allies in exposed places who still rely for their safety on America’s nuclear umbrella.

Instead the review repeats a past pledge that America will not use nuclear weapons against states that do not have them and are in compliance,Mr Obama says,with their commitments under the Nuclear Non-Proliferation Treaty. That leaves Iran,Syria and others suspected of illicit nuclear dabbling still theoretically on the potential target list. Yet Mr Obama has also ruled out,as Mr Bush never did,nuclear retaliation against chemical,biological or cyber attacks by the nuclear have-nots — unless,that is,America’s fundamental security or that of its allies is at risk.

He agrees with Mr Bush that America can make deep cuts in the weapons stocks it keeps in reserve to hedge against technical failure or a surprise new threat. Mr Bush would have done this while building fewer,but more modern,replacement nuclear warheads. Mr Obama prefers instead to refurbish some existing ones. He also plans to upgrade further America’s nuclear-weapons labs and other facilities. The vice-president,Joseph Biden,has called the labs “national treasures”. Mr Obama’s budget includes $624m beyond the sum Congress earmarked last year for such work,with more to come over five years.

But already there are grumbles. The extra cash has not stopped the labs’ directors asking for more. Mr Obama needs their support. For he intends to do something Mr Bush refused to do: to work to win Senate ratification of the Comprehensive Test-Ban Treaty (CTBT),which was rejected on a partisan vote in 1999.

The leader of the attack last time was Arizona’s Jon Kyl,still a Republican senator. Mr Kyl insists,as he did then,that a CTBT is unverifiable — and,by banning future testing,puts America’s nuclear safety and security at risk. In fact,America has not felt any need to test its bombs since 1992. Advances in high-speed computing and other technologies allow today’s labs to solve problems that actual weapons tests never could. Meanwhile,the treaty’s global monitoring system is now a reality. Unlike other enemies,however,Mr Kyl is undeterred.