Cast your mind back to the last time you played Monopoly with a sore loser.
He - and it's always a he - insists on being banker. He declares your family tradition of stashing all the fines in Free Parking to be against the rules. His pile of cash and houses seems to grow every time someone goes to get another bag of crisps, or pops to the loo.
Then one player he has driven to the brink of bankruptcy lands on Free Parking, and scoops the jackpot. The balance of the game swings away from the bully. He is found in breach of the rules himself. The others co-ordinate against him, and dad - it's always dad - gifts his cash and assets to the person most likely to destroy the aggressor.
When he buys hotels no-one visits, is jailed and unable to take rent, when the lie that he was All-England Monopoly Champion 1984 is finally disproved, and he has been reduced to being little more than a tiny, pewter boot, he flips the board in a fury.
We've all played with that guy. And picked up the pieces afterwards. We all know there was never any point in helping him to lose more gently so that he could save face. He needed to lose - and for everyone to know it.
The wheels have been ripped off Vladimir Putin's unserviced trucks. The tanks have been immobile on the roads, and have now gone off-road to become immobile in the mud. Goliath's planes and helicopters have been shot down by David's surface-to-air missiles, and the children Putin sent to war have died in such numbers he's been forced to order up mercenaries and Bashar al Assad's surviving conscripts.
He's shut down the TV stations, lost his Big Macs, and destroyed the mobile phone masts which his own intelligence forces were using to communicate. His generals are dying on the frontline because they had to abandon the control room to get their orders followed. He restructured Russia's economy to be based on energy extraction and supply, and half the world's stopped buying it overnight. The only people choosing to be on his side are the thicker end of the Chelsea terraces.
Nothing in those previous two paragraphs happens when you're winning. And if it happens in the space of two weeks, the board-flipping moment when Putin realises his own failure cannot be far off.
But what's worrying the West is what he'll do to distract from the loss. Will he mine or gas Ukraine as he retreats? Will he fire tactical, smaller nukes which will obliterate buildings, irradiate the concrete dust sucked into the fireball, and then allow microscopic, inhalable radioactive particles to fall gently along the routes of prevailing winds? Perhaps he will release any one of the deadly pathogens he holds within the world's largest bioweapon stockpile.
That's why world leaders, analysts, and journalists talk about an "off-ramp", giving the madman an exit where he can make a dignified withdrawal and save face. They want him to think he can keep his job and his billions if only he de-escalates, and steps back from the brink.
The problem with that is a madman in a tank doesn't give a s*** about the rules of the road. The point at which he was sane enough to spot and take an exit route was waaaaaaaay back, before he lost his mind. If this guy saw an off-ramp now, he'd bomb it.
If Putin is capable of using unimaginably-bad weapons - and he is - then he is adrift from the reality he would need to have any instinct of self-preservation. The flipping of the board is as certain as the coup d'etat the oligarchs he created will stage to save their looted billions. The issue with both is not if, but when.
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If it happens soon, thousands and maybe millions of lives can be saved. The Russian economy can recover, and the world can help Ukraine pick up the pieces. To act against Putin, his deposer needs to be more realistic and practical than he is, which is why it would work in the world's favour and is perhaps also why it hasn't happened yet among the men he has manipulated and paid off for two decades.
That's the end-game the world and its leaders must seek, because Putin is past the point of saving his own face. He would happily saw it off himself, then threaten to do everybody else's, if you let him have so much as a butter knife.
The world needs him to lose. To have no exit, and to know it. All despots must see what happens if you invade a sovereign nation, and that the West's immense financial power, whether in the shape of official sanctions or a spontaneous customer boycott, is a weapon with no possible defence.
Because he was always going to flip the board one day, if you let him play. Giving him an off-ramp means he's still mad, and he's still got a tank. Letting him slice off a piece of Ukraine is like letting him go bankrupt, but keep a hotel on Mayfair.
We should never have sat down with someone who has never obeyed, but only imposed, rules. We are counting the cost of making money while he picked on someone else. But the only upside of playing a game with a sore loser is that, when he loses, he feels sorest.
Economically throttling his cronies is the swiftest, best and only weapon we can use, because they want to keep playing this game. Our best hope is that Putin realises he's lost when the board, and all the lives on it, are no longer within his reach.