LONDON. — London.
Will we live to see nuclear war? What only a year ago seemed totally remote, the door on the Cold War closed forever, now creeps up on us by an unmarked trail.
It is alleged that Iraq might be able to explode a primitive nuclear device. Strategists talk of the need for tactical nuclear weapons if a land offensive gets bogged down at the same time Iraq is intimidating the allied forces and Israeli cities with chemical and biological weapons. When questioned, top officials in both the U.S. and British Administrations refuse to rule out the right to go nuclear. Only President Francois Mitterand replies unambiguously, ''I say no to that.''
This is a dangerous debate of the highest order, whose effects inevitably work to lower the sacrosanct threshold that in historian C.P. Thompson's telling remark allows ''the unthinkable to become thinkable, without thinking.''
Since the Cuban Missile Crisis Western public opinion -- and Soviet too -- has been constantly reassured that nuclear weapons were only to deter, not to be used. If they were used, everyone seemed to understand, the game was lost.
When President Jimmy Carter's National Security Advisor, Zbigniew Brzezinski told me in a widely quoted interview that in an all-out nuclear war only ''about 10 percent of humanity would be killed . . . . descriptively and analytically it's not the end of humanity,'' he was attacked on all sides. Soviet President Leonid Brezhnev took him to task for breaking the implicit understanding between Moscow and Washington that nuclear war was too terrible to contemplate.
The single most graphic counter to nuclear war was provided by Lord Mountbatten, a man who knew as much about war first hand as any man alive: ''And when nuclear war is all over what will the world be like? Our fine great buildings, our homes will exist no more. The thousands of years it took to develop our civilization will have been in vain. Our works of art will be lost. There will be no hospitals. No help can be expected for the few mutilated survivors in any town to be sent from a neighboring town -- there will be no neighboring towns left, no neighbors. There will be no help. There will be no hope.''
Of course, one primitive bomb trucked to the border with Saudi Arabia and detonated would not be the end of civilization. Neither would a low yield nuclear weapon, launched on a cruise missile aimed at the concentrated formations of the Republican Guard.
Iraq is not the Soviet Union with an arsenal of 20,000 nuclear warheads. There does not exist in the Middle East the dangerous possibility of the ''ladder of escalation'' that until recently dominated military thinking on the East/West border in Europe. If one side started with one small battlefield nuclear shell the other, it was assumed, would retaliate with a somewhat bigger one and before the day was over the long range intercontinental city- decimators would be in flight.
But there is a much more insidious ladder of escalation around the corner. Saddam Hussein uses his dirty bomb, gas or biological weapons on the battlefield or sends suicide bombers with a one way ticket to Israel armed with chemicals.
In themselves, given the degree of protection and the problems of delivery, none of these, apart from the nuclear weapon, will cause much physical danger. But in the heat of a ground attack that is not going well they can effect morale badly. Imagine too if all this happens simultaneously and, moreover, the attack on Israel triggers a massive resurgence of the intifada. In such a situation President George Bush may give the order to fire a nuclear missile if only to pre- preempt a larger Israeli attack.
The war ends. But then at least three countries in the Muslim world would go nuclear within a couple of years. Pakistan comes out of its closet with its already manufactured bomb. Only last week Pakistan's powerful army chief turned the tables on his own government and termed the war a Zionist plot against Islam. Pakistan also makes the bomb available to Saudi Arabia which, att preempting to placate its public opinion, revolted by U.S., British and Israeli excesses in the war, decides on Saudi self-sufficiency. The Saudis mount these new weapons on their CSS-2 rockets purchased two years ago from China and described at the time by the authoritative International Institute for Strategic Studies as ''difficult to justify in terms of range, payload and cost unless they carry nuclear weapons.''
Egypt too will feel it needs the bomb and steps up its joint research program with Argentina to build an 800-kilometer range, nuclear-carrying missile, the Condor 2. Argentina may have made its nuclear peace last year with its continental rival, Brazil, but frankly it needs the money foreign sales could bring in.
If the allies or Israel end up making nuclear weapons the currency of power in the Middle East and tearing up the post-Hiroshima inhibition on their use then we can be sure that it will be only a matter of a few years before they are used again. But this time the armories will be much bigger. And who is to say that some of the missiles won't be targeted on nearby southern Europe -- any member of the European Community or NATO would be a convenient hostage.
This is the Pandora's Box that we are in danger of opening. Messrs. Bush, Major, Shamir, it's better you speak up at once: ''I say no to that.''
Jonathan Powell writes a column about the Third World.