After a year and a half of unrelenting gloom, finally news for Ukrainians to celebrate.
Open conflict between their enemies and the prospect of much more.
Ukrainians have always predicted this war would be the end of Vladimir Putin.
Ukraine war latest: Putin calls rebellion ‘treason’
Last year, their head of military intelligence told Sky News it would finish the Russian leader and his country’s unity.
Ukraine’s national security chief Oleksiy Danilov said today that the Wagner mutiny had started the “process of Russia’s self-destruction”.
“As the war began, so it will end – in Russia,” he added.
Wagner’s head Yevgeny Prigozhin has said the war effort goes on even though he has, it seems, taken control of one of its key headquarters in Rostov-on-Don.
But the impact of red-on-red fighting back home on Russian soldiers in trenches facing a Ukrainian counter-offensive can only be guessed at.
Russian troops have complained bitterly that their government has armed and trained them poorly.
They have died in their tens of thousands, many reportedly shot by their own side, and among those fighting on, morale is likely to be low.
Read more:
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Who is Yevgeny Prigozhin and why does Putin feel threatened by him?
It remains to be seen whether they remain loyal to the Kremlin or can be seduced by Prigozhin to switch.
It is early days and nothing is quite what it seems in Russia.
But we can say for sure that this will undermine Russia’s war effort, not least because thousands of its most effective fighters in the Wagner Group appear to have left the theatre of war to launch an armed rebellion on home soil.
Long term, the outlook may not be so encouraging.
Yes, Putin is most likely terminally weakened by this.
The war that he started and was meant to last a few weeks is mutating into a civil conflict.
If he is toppled his most likely successors are even more hardline than him.
They are likely to continue the war if they can.
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Equally, Prigozhin is a brutal, volatile man who actually knows how to wage a war and whose supporters are battle hardened and full of hatred for Ukraine.
He would not be an easy enemy for Ukraine if he were to succeed Putin although that for now seems against the odds.
Ukrainians will be hoping for a protracted period of internal conflict that fatally undermines Russia’s ability to fight this war or forces whoever ends up in charge in Moscow to bring it to an end.