The world is facing a growing threat of nuclear war

Within the next few weeks, after years of stalling and evasion, Iran may at last agree to curb its nuclear programme.

In exchange for relief from sanctions it will accept, in principle, that it should allow intrusive inspections and limit how much uranium will cascade through its centrifuges.

After 2025 Iran will gradually be allowed to expand its efforts. It insists these are peaceful, but the world is convinced they are designed to produce a nuclear weapon.

In a barnstorming speech to America's Congress on March 3rd, Binyamin Netanyahu, Israel's prime minister, fulminated against the prospect of such a deal (see page 41). Because it is temporary and leaves much of the Iranian programme intact, he said, it merely "paves Iran's path to the bomb". Determined and malevolent, a nuclear Iran would put the world under the shadow of nuclear war.

Mr Netanyahu is wrong about the deal. It is the best on offer and much better than no deal at all, which would lead to stalemate, cheating and, eventually, the dash to the very bomb he fears. But he is right to worry about nuclear war--and not just because of Iran.

Twenty-five years after the Soviet collapse, the world is entering a new nuclear age. Nuclear strategy has become a cockpit of rogue regimes and regional foes jostling with the five original nuclear-weapons powers (America, Britain, France, China and Russia), whose own dealings are infected by suspicion and rivalry.

Thanks in part to Mr Netanyahu's efforts, Iran commands worldwide attention. Unfortunately, the rest of the nuclear-weapons agenda is bedevilled by complacency and neglect.

The fallout from Prague

After the end of the cold war the world clutched at the idea that nuclear annihilation was off the table. When Barack Obama, speaking in Prague in 2009, backed the aim to rid the world of nuclear weapons, he was treated not as a peacenik but as a statesman. Today his ambition seems a fantasy. Although the world continues to comfort itself with the thought that mutually assured destruction is unlikely, the risk that somebody somewhere will use a nuclear weapon is growing apace.

Every nuclear power is spending lavishly to upgrade its atomic arsenal. Russia's defence budget has grown by over 50% since 2007, and fully a third of it is devoted to nuclear weapons: twice the share of, say, France. China, long a nuclear minnow, is adding to its stocks and investing heavily in submarines and mobile missile batteries.

Pakistan is amassing dozens of battlefield nukes to make up for its inferiority to India in conventional forces. North Korea is thought to be capable of adding a warhead a year to its stock of around ten, and is working on missiles that can strike the west coast of the United States. Even the Nobel peace laureate in the White House has asked Congress for almost $350 billion to undertake a decade-long programme of modernisation of America's arsenal.

New actors with more versatile weapons have turned nuclear doctrine into guesswork. Even during the cold war, despite all that game theory and brainpower, the Soviet Union and America frequently misread what the other was up to. India and Pakistan, with little experience and less contact, have virtually nothing to guide them in a crisis but mistrust and paranoia. If weapons proliferate in the Middle East, as Iran and then Saudi Arabia and possibly Egypt join Israel in the ranks of nuclear powers, each will have to manage a bewildering four-dimensional stand-off.

Worst of all is the instability. During much of the cold war the two superpowers, anxious to avoid Armageddon, were willing to tolerate the status quo. Today the ground is shifting under everyone's feet.

Some countries want nuclear weapons to prop up a tottering state. Pakistan insists its weapons are safe, but the outside world cannot shake the fear that they may fall into the hands of Islamist terrorists, or even religious zealots within its own armed forces. When history catches up with North Korea's Kim dynasty, as sooner or later it must, nobody knows what will happen to its nukes--whether they might be inherited, sold, eliminated or, in a last futile gesture, detonated.

Others want nuclear weapons not to freeze the status quo, but to change it. Russia has started to wield nuclear threats as an offensive weapon in its strategy of intimidation. Its military exercises routinely stage dummy nuclear attacks on such capitals as Warsaw and Stockholm. Mr Putin's speeches contain veiled nuclear threats. Dmitry Kiselev, one of the Kremlin's mouthpieces, has declared with relish that Russian nuclear forces could turn America into "radioactive ash".

Just rhetoric, you may say. But the murder of Boris Nemtsov, an opposition leader, on the Kremlin's doorstep on February 27th was only the latest sign that Mr Putin's Russia is heading into the geopolitical badlands (see page 33). Resentful, nationalistic and violent, it wants to rewrite the Western norms that underpin the status quo.

First in Georgia and now in Ukraine, Russia has shown it will escalate to extremes to assert its hold over its neighbours and convince the West that intervention is pointless. Even if Mr Putin is bluffing about nuclear weapons (and there is no reason to think he is), any nationalist leader who comes after him could be even more dangerous.

Towards midnight

China poses a more distant threat, but an unignorable one. Although Sino-American relations hardly look like the cold war, China seems destined to challenge the United States for supremacy in large parts of Asia; its military spending is growing by 10% or more a year. Nuclear expansion is designed to give China a chance to retaliate using a "second strike", should America attempt to destroy its arsenal.

Yet the two barely talk about nuclear contingencies--and a crisis over, say, Taiwan could escalate alarmingly. In addition Japan, seeing China's conventional military strength, may feel it can no longer rely on America for protection. If so, Japan and South Korea could go for the bomb--creating, with North Korea, another petrifying regional stand-off.

What to do? The most urgent need is to revitalise nuclear diplomacy. One priority is to defend the nuclear Non-Proliferation Treaty, which slows the spread of weapons by reassuring countries that their neighbours are not developing nukes. It was essential that Iran stayed in the treaty (unlike North Korea, which left).

The danger is that, like Iran, signatories will see enrichment and reprocessing as preparation for a bomb of their own--leading their neighbours to enrich in turn. That calls for a collective effort to discourage enrichment and reprocessing, and for America to shore up its allies' confidence.

You don't have to like the other side to get things done. Arms control became a vital part of Soviet-American relations. So it could between China and America, and between America and Putin's Russia. Foes such as India and Pakistan can foster stability simply by talking. The worst time to get to know your adversary is during a stand-off.

In 1960 Albert Wohlstetter, an American nuclear strategist, wrote that, "We must contemplate some extremely unpleasant possibilities, just because we want to avoid them." So too today, the essential first step in confronting the growing nuclear threat is to stare it full in the face.

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