The breach of the Nova Kakhovka dam is most worrying for what it says about the mind of Russian President Vladimir Putin and his generals – and their capacity for dangerous escalation.
It takes the war in an even more perilous direction.
The military impact is likely to be temporary. Armies blow dams or use them to unleash floodwaters for tactical advantage.
The Soviets and the Germans both did it in the Second World War.
But the gains generally do not hold. Water drains away, the ground dries out.
Ben Barry, a land war senior fellow at the International Institute of Strategic Studies, said: “It could set back any assault river crossing for a couple of weeks.
“Difficult to tell for how long. But only once the water subsides and the ground dries out will Ukraine have the same chance of a river crossing as it did before the flood.”
And he believes an attack across the swollen Dnipro is not out of the question even now.
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“It’s not impossible to do an assault river crossing across a river that’s in full flood. It’s just more difficult,” he said.
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2:57
Kherson main square ‘awash with water’
The Russians have blamed the Ukrainians for the attack, but most analysts have dismissed that as unlikely to impossible.
The Russians have a proven track record for accusing the other side of doing what they have themselves done. And the Russians have most to gain. Up to a point.
The breach benefits the Russians by reducing the length of the frontline it has to defend and allowing it to focus attention in the east, but not indefinitely.
And it has blowback for the Russians too, flooding some of the defensive positions they have dug in on the southern bank since retreating there last August.
So temporary gain, some self-harm and all the opprobrium that comes with carrying out yet another war crime.
Where is the margin in that for Vladimir Putin? It looks rash and premature. A disproportionate and irrational act.
But that may be the point.
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3:27
Ukraine dam attack explained
Russian president ‘excels in scare tactics’
In war, it can pay to do the crazy thing, to look unhinged and keep your enemy guessing at your next act of madness.
Putin excels in scare tactics and knows the dam blast makes him look more dangerous.
If Russia was irresponsible enough to blow the dam and unleash such destruction for limited advantage, what will it do next, planners in Kyiv and the West will be asking.
The fear now is for the Zaporizhzhia nuclear power plant. The dam breach endangers the supply of water to its cooling systems. Could Russia now sabotage the plant to change the course of the war?
The destruction of the dam undoubtedly changes the risk calculus in handling Russia, but correctly calibrating it will need cool heads so it is not overdone.
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1:31
Ukraine war: Major dam attack
Putin has, after all, indulged in nuclear sabre-rattling for much of this war.
It has weighed on the minds of Ukraine’s allies and made them more timid in arming Kyiv.
But so far analysts say his nuclear bluster is just that.
Image: The Zaporizhzhia nuclear power plant. Pic: File
The nuclear option
There is no sign of Putin starting the lengthy process of bringing tactical warheads out of storage and deploying them.
And any disaster at Zaporizhzhia threatens Russia most.
The prevailing winds would be most likely to carry the fallout east across the Russian border.
The Russians have shown stunning disregard for the welfare of their own soldiers but a radioactive cloud over their defensive positions and logistics lines would be challenging to say the least.
What we can say for sure is this war has swung again in a more unpredictable direction and the longer it goes on, the more such lurches are likely to happen.
America appears to have hit the three key locations in Iran’s nuclear programme.
They include Isfahan, the location of a significant research base, as well as uranium enrichment facilities at Natanz and Fordow.
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Natanz was believed to have been previously damaged in Israeli strikes after bombs disrupted power to the centrifuge hall, possibly destroying the machines indirectly.
However the facility at Fordow, which is buried around 80 metres below a mountain, had previously escaped major damage.
Details about the damage in the US strikes is not yet known, although Mr Trump said the three sites had been “obliterated”.
The US has carried out a “very successful attack” on three nuclear sites on Iran, President Donald Trump has said.
The strikes, which the US leader announced on social media, reportedly include a hit on the heavily-protected Fordow enrichment plant which is buried deep under a mountain.
The other sites hit were at Natanz and Isfahan. It brings the US into direct involvement in the war between Israel and Iran.
Israeli Prime Minister Benjamin Netanyahu hailed the “bold decision” by Mr Trump, saying it would “change history”.
Iran has repeatedly denied that it is seeking a nuclear weapon and the head of the UN’s nuclear watchdog said in June that it has no proof of a “systematic effort to move into a nuclear weapon”.
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3:34
Trump: Iran strikes ‘spectacular success’
Addressing the nation in the hours after the strikes, Mr Trump said that Iran must now make peace or “we will go after” other targets in Iran.
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Commenting on the operation, he said that the three Iranian sites had been “obliterated”.
“There will be either peace or there will be tragedy for Iran far greater than we have witnessed over the last eight days,” he said.
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1:20
Benjamin Netanyahu said Donald Trump and the US have acted with strength following strikes on Iran’s nuclear facilities.
In a posting on Truth Social earlier, Mr Trump said, “All planes are safely on their way home” and he congratulated “our great American Warriors”. He added: “Fordow is gone.”
He also threatened further strikes on Iran unless it doesn’t “stop immediately”, adding: “Now is the time for peace.”
It is not yet clear if the UK was directly involved in the attack.
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Among the sites hit was Fordow, a secretive nuclear facility buried around 80 metres below a mountain and one of two key uranium enrichment plants in Iran.
“A full payload of BOMBS was dropped on the primary site, Fordow,” Mr Trump said. “Fordow is gone.”
There had been a lot of discussion in recent days about possible American involvement in the Iran-Israel conflict, and much centred around the US possibly being best placed to destroy Fordow.
Meanwhile, Natanz and Isfahan were the other two sites hit in the US attack.
Natanz is the other major uranium enrichment plant in Iran and was believed to have possibly already suffered extensive damage in Israel’s strikes earlier this week.
Isfahan features a large nuclear technology centre and enriched uranium is also stored there, diplomats say.
Israelis are good at tactics, poor at strategic vision, it has been observed.
Their campaign against Iran may be a case in point.
Short termism is understandable in a region that is so unpredictable. Why make elaborate plans if they are generally undone by unexpected events? It is a mindset that is familiar to anyone who has lived or worked there.
And it informs policy-making. The Israeli offensive in Gaza is no exception. The Israeli government has never been clear how it will end or what happens the day after that in what remains of the coastal strip. Pressed privately, even senior advisers will admit they simply do not know.
It may seem unfair to call a military operation against Iran that literally took decades of planning short-termist or purely tactical. There was clearly a strategy of astonishing sophistication behind a devastating campaign that has dismantled so much of the enemy’s capability.
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3:49
How close is Iran to producing a nuclear weapon?
But is there a strategic vision beyond that? That is what worries Israel’s allies.
It’s not as if we’ve not been here before, time and time again. From Libya to Afghanistan and all points in between we have seen the chaos and carnage that follows governments being changed.
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Hundreds of thousands have died. Vast swathes of territory remain mired in turmoil or instability.
Which is where a famous warning sign to American shoppers in the 80s and 90s comes in.
Ahead of the disastrous invasion that would tear Iraq apart, America’s defence secretary, Colin Powell, is said to have warned US president George W Bush of the “Pottery Barn rule”.
The Pottery Barn was an American furnishings store. Signs among its wares told clumsy customers: “You break it, you own it.”
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0:36
Iran and Israel exchange attacks
Bush did not listen to Powell hard enough. His administration would end up breaking Iraq and owning the aftermath in a bloody debacle lasting years.
Israel is not invading Iran, but it is bombing it back to the 80s, or even the 70s, because it is calling for the fall of the government that came to power at the end of that decade.
Iran’s leadership is proving resilient so far but we are just a week in. It is a country of 90 million, already riven with social and political discontent. Its system of government is based on factional competition, in which paranoia, suspicion and intense rivalries are the order of the day.
After half a century of authoritarian theocratic rule there are no opposition groups ready to replace the ayatollahs. There may be a powerful sense of social cohesion and a patriotic resentment of outside interference, for plenty of good historic reasons.
But if that is not enough to keep the country together then chaos could ensue. One of the biggest and most consequential nations in the region could descend into violent instability.
That will have been on Israel’s watch. If it breaks Iran it will own it even more than America owned the disaster in Iraq.
Iran and Israel are, after all, in the same neighbourhood.
Has Israel thought through the consequences? What is the strategic vision beyond victory?
And if America joins in, as Donald Trump is threatening, is it prepared to share that legacy?
At the very least, is his administration asking its allies whether they have a plan for what could come next?