WE forgot about nuclear weapons.

After the collapse of the Soviet Union 20 years ago we fell into a willed amnesia while politicians talked – though not for long – about a “peace dividend” and a new world order. Some of them spoke as though they believed it.

That was almost forgivable. The Cold War had ended and only a single superpower remained. Surely there was no longer a reason to worry about missiles hurtling above the polar ice, or falling on the Clyde. Even the most paranoid of right-wing Americans had been deprived of an excuse. So the rest of us lapsed, gratefully and instantly, into forgetfulness.

That too was forgivable. Those of us whose dim memories began with the Cuban missile crisis were entitled, I think, to hope for the best. The feeling is difficult to convey to a younger generation. Let’s just say that if your entire life, child to adult, has been bounded by the realistic expectation of infernal lunacy, you don’t quibble with peace.

Or even, as things turned out, with the appearance of peace. I have a theory about that. Sometimes I think the absence of “nuclear exchanges” only made it easier for politicians to contemplate conventional warfare. It was as though by avoiding one taboo they were free to flout all others. We’ve had a lot of that since the end of the first Gulf conflict in 1991.

Iraq has come and (for now) gone. Afghanistan has passed the 10-year mark. Nato has launched itself on Libya, for good reasons and bad, as though at the drop of a hat. Without the risk of mutually assured destruction none of it seemed so terrible, at least to those making the decisions.

The rest of us went on forgetting about nuclear weapons. We forgot that they hadn’t gone away, and hadn’t been put beyond use. We failed to notice that the treaties and trumpeted non-proliferation agreements had been in essence cosmetic: the machinery for extermination remained in working order. Only when the contradictions became preposterously obvious did we briefly pay attention.

Saddam has weapons of mass destruction, you say? So what is it that we possess, and refuse to give up until, like some stand-off in an old western, everyone else lays down their shooting irons? Britain needs to renew Trident, you say? Whom do we propose to fight? In what sense would such a fight end well? And why are we lecturing others on the horrors of nuclear arms?

One school of thought says the threat may actually be greater now than it ever was. Iran certainly seems hell-bent on providing proof. But several regimes grasped the logic long before Tehran felt the need for a thermo-nuclear cod-piece. Israel awarded itself nukes when none of its neighbours possessed them. India and Pakistan set off on a two-horse race in the 1970s. North Korea long ago demonstrated that even a lunatic regime gets “respect” if it owns a bomb.

Iran’s case is held to be more dangerous than any of these. A regime that is far from secure, and far from popular, might seek national unity through aggression. Its madcap president, Mahmoud Ahmadinejad, has spoken often enough of eradicating Israel, and of teaching the United States a lesson. Iran has few enough friends, meanwhile, in the Muslim world. Saudi Arabia is as fearful as anyone about Tehran’s nuclear weapons programme.

That programme is not supposed to exist, of course. Officially, all nuclear work is for peaceful purposes. To suggest otherwise is an insult, and evidence of a plot against the Iranian people. Or as Ahmadinejad has said: “The Iranian nation will not succumb to bullying, invasion and the violation of its rights.” Both the International Atomic Energy Authority (IAEA) and the UN dismiss this posturing. Iran, they believe, is two or three years away from “weaponising” its missiles.

Israel sees no contradiction between possessing its own nuclear arsenal and refusing to countenance this state of affairs. America refuses to countenance anything that Israel will not tolerate – a presidential election is on the way – while Britain makes “contingency” plans to tag along behind the US. So the madness resumes.

A pre-emptive Israeli raid on Iran will not make the world a safer place. A nuclear-armed Tehran would make that world a vastly more dangerous place. American support for an Israeli attack will anger Russia and China, countries reluctant to impose fresh sanctions against Iran, and destroy all hope of peace in the Middle East. That’s supposing the mullahs do not already possess a working doomsday toy.

When Barack Obama came to office he said he wanted to rid the world of nuclear weapons. He did add, though, that America would not be disposing of its own stockpile – 5000-plus warheads – if others did not follow suit. Last April he signed another arms control treaty with the Russians and declared that another new era had begun. This was just weeks after the president had asked Congress for $7 billion – an increase of $624 million – for “nuclear weapons-related activities”.

Some 45 million Americans were living below the poverty line when Obama made his request. It was not war-like, according to the head of the National Nuclear Security Administration, Thomas D’Agostino. The US was moving, he said, from “a Cold War nuclear weapons complex ... into a 21st-century, nuclear security enterprise”. Spot, if you will, the difference.

But the Russians also retain 5000-plus warheads to meet, in Vladimir Putin’s words, “the demands of the modern world”. Britain has a couple of hundred weapons for its Trident boats; France perhaps 300 warheads; China perhaps 250; India and Pakistan may have 100 or so each; Israel could have anywhere between 75 and 200. All in all, if you count the weapons stockpiled by the US and Russia that are not ready for immediate use, there are probably 22,000 warheads in the world.

India, Pakistan and North Korea refused to sign the 1968 Nuclear Non-Proliferation Treaty. They objected to being controlled by countries that were and remain armed to the teeth. Israel, in a revealing parallel with Iran, refuses to confirm or deny the existence of a weapons programme, and does as it pleases.

The fundamental problem is this: having failed to disarm, the nuclear club of five – the US, Russia, Britain, China and France – are the worst possible advocates of disarmament. Add the failure to halt proliferation – why wasn’t Israel stopped? – and every regime has its excuse. The five are hypocrites. The five use talk of a “nuclear threat” as an excuse to dominate fledgling powers. Tehran knows the script.

The charge of hypocrisy is accurate. What are the five saying, after all? Simply this: we can be trusted with these horrific weapons, but you cannot. We’ll get rid of these weapons one day, but only when it suits us.

Yet here’s the quandary: who does trust Iran? The IAEA has been patient. Diplomatic efforts have been going on for years. The Iranians have been alternately dishonest and bellicose. They don’t sound as though they seek a sabre just for the rattling noise.

So Israel itches to bomb “by Christmas”. Will that help? Conventional weapons are allowed, are they not? Or do they just persuade every country in the Middle East with the means that a nuclear weapons programme is a priority?