Nuclear war is not “unthinkable”. Military planners spend a lot of time thinking about and planning for it. We are now closer to it than at any time this century.

President Zelensky of Ukraine is making continual calls for NATO to try to impose a “No Fly Zone” over Ukraine. War reporters elicit similar appeals from people on the ground, giving it a moral charge that builds pressure for it. It is possible that this is being done on the delusion that the consequences are so severe that it can’t happen; that no one in their right mind would sanction it. But the logic of war is escalation. And the people running it are not always in their right mind. Rehearsing something, even as a fantasy, can be preparation for doing it.

In case there is any doubt about what a No Fly Zone would mean, Former NATO Supreme Allied Commander of Europe, General Philip Breedlove has spelt it out “If you put a no-fly zone in the eastern part of Ukraine … and we’re going to fly coalition or NATO aircraft into that no-fly zone, then we have to take out all the weapons that can fire into our no-fly zone and cause harm to our aircraft. So that means bombing enemy radars and missile systems on the other side of the border [i.e. Russia].That is tantamount to war.” General Breedlove is, we should note, in favour of doing this. And he is not alone, if media pundits on US talk shows are anything to go by.

If an action is “tantamount to war” between NATO and the Russian Federation, we should all be clear that a nuclear exchange becomes more likely than not and understand why.

Russia does not have a “no first use” policy for its nuclear weapons, and carried out drills for them just before the invasion, with an explicit warning to NATO not to get involved.

US nuclear war policy is, and always has been, based on a devastating first strike. The first iteration of this was their Strategic Integrated Operations Plan of 1960, in which a conventional war with the USSR would trigger the US smashing every city in Eastern Europe, Russia and China with 3,400 nuclear warheads; killing 600 million people (200 million of them collateral damage in Western Europe, Japan, India and other places close enough to the targets to be impacted) in a matter of hours. That would have been one person in 5 of the total global population at the time. There is no reason to believe that subsequent reiterations of this plan are any less restrained.

Having the two powers with the world’s greatest stockpiles of nuclear weapons, primed and ready, in an open conflict and incredibly nervous that the other is going to strike them first, means that we would be a nerve shredding hair trigger away from mutually assured destruction. No exchange of these missiles would be cautious or incremental, or slow. It would be all or nothing and very fast. All and nothing.

Whatever anyone’s view of this war, the reasons for it, or the way it could best and most swiftly be brought to an end; recognition that anyone calling for a No Fly Zone is inviting us to Armageddon should be seared into all of us and resolutely opposed.