Here's abc's tom Sufi burge.

Now with the latest this week, a major breakthrough for Ukraine in the Northeast.

Its forces advancing quickly through the Russian lines, wrecked Russian vehicles lining the roads.

Russian forces caught off guard apparently in disarray, Ukrainian troops liberating cities and the Ukrainian flag flying.

Once again, a senior Ukrainian official telling abc news.

The operation was thoroughly planned and everything was running to schedule overnight.

President Zelensky saying his forces have liberated over 700 square miles of territory in just the past 10 days claiming Russian troops were running away calling it a good choice.

The biggest prize so far, Ukrainian forces entering the strategically important city of Siem.

Without Izzy um Putin's goal of capturing all of Ukraine's neighboring eastern Donbass region will be even harder in newly liberated villages.

Ukrainian police digging up bodies.

Fresh war crimes investigations now underway this week, Ukrainian military command saying drones are playing a crucial role in counter offenses in the east and the south were with a Ukrainian reconnaissance unit just outside Asia.

And these guys main job is to work out where the Russian positions are so they can call in the strikes and this morning a real sense of crisis at the zap or Asia nuclear power plant, the last remaining reactor shut down overnight, shelling in the area, cutting off the last remaining x external power supply.

So the plant is now only stable because of diesel generators and the risk of a nuclear catastrophe real.

The UN's nuclear watchdog with officials now based at the plant.

With this desperate appeal, a nuclear power plant can never be a pawn of war.

It's fate must not be decided by military means Martha.

What's striking about this advance is the speed at which the Ukrainian military has been taking territory.

It also seems that the Ukrainians have captured a ton of abandoned Russian military equipment and ammo another sign that the Russians left in a hurry.

This is a protracted war.

It probably has a long way to run.

But this is a really big moment.

Martha Tom Sufi Burge in Ukraine.

Thanks to him.

Let's bring in our chief foreign correspondent, Ian Pannell, who joins us now and Ian you have spent more time in Ukraine than anyone.

This is a pretty extraordinary turn of events.

How significant do you see it?

Yeah, I agree, I think is the most significant event since the Russians were forced to withdraw from around the cap Back in April earlier this year at the time.

They talked about it being a reallocation of troops are regrouping, they're using the same phrases now, this is huge.

The amount of territory they've taken is more than 3000 square kilometers, something like over 1100 square miles in a matter of days.

A number of factors.

I think the key one was the Ukrainians announced that they were going to target their offensive in the south in her som and that led to the Russians pulling a lot of their best forces away from the zoom away from these areas around hockey, relocated them there.

So they were vulnerable.

They didn't backfill, they didn't have the support there.

And the Ukrainians planned, they saw the weakness and they struck and the Russians have lost massive amounts of equipment.

Their supply lines have broken down because of this.

So what do they do now?

And what does Vladimir Putin?

The options don't look great.

I mean there are very very few.

They're in real trouble right now.

They're in defensive positions everywhere because what this offensive means.

It doesn't just mean the north of the country, it frees up Ukrainian troops to now push down into Dom Batt.

Remember we're all talking about the east of the country, all that territory that the Ukrainians that Ukraine's had to cede to the Russians.

Well now the Ukrainians are on the front foot looking like they may retake some of those key places.

We talked about the Russians taking Luhansk which is one half of the Donbass.

Well now they don't have it anymore.

They have, the majority of it, but they're still on the back foot.

Putin does not have many good options.

We've talked about this over and over again as being a war of attrition.

It still is this does not end anything on one level.

It doesn't.

But I think what it shows us and what should teach us is it's not a static conflict.

It is a war of attrition.

But every time one side or another makes again we leap from one direction to the other saying the Russians are on the front foot, took the Donbass.

The Ukrainians having real problems.

Well now it looks the other way around.

I genuinely believe that Russia has a much bigger problem here.

It can't resupply its troops.

It doesn't troop rotations, it's lacking in the equipment and the ammunition.

And as I say, they're on the defensive everywhere.

The Ukrainians are getting huge help from the United States and other countries And they know that they've got the momentum on their side.

And I do want to turn to the death of the queen.

I know you first met her.

You told us a wonderful story about first meeting her in 1993 is a very young reporter, I'm sure.

And also king Charles when he was Prince, you were in Afghanistan.

This is really a time of reckoning for him.

What do you see?

Yes, I mean, he's got huge shoes to fill.

What struck me about meeting the queen was her ability to put people at ease to touch everybody and to kind of fill a room with her presence and kind of Sprinkle royal fairy dust if you like, Charles has got a much bigger problem because he doesn't have the credit in the bank that his mother did, that the queen did.

And he will be under a lot of pressure, a lot of scrutiny in the But what I learned in Afghanistan is his public figure.

He can seem rather aloof, rather stuffy.

But actually, when you talk to him, he's very engaged and very engaging.

He knows his topic is very good at meeting people, but his sons served as well.

Both of his sons served.

But he's led a very privileged life and Britain has changed substantially since when his mother was coronated.

He will have to meet that challenge.

It's always great to see you Ian Pannell, wherever we are in the world.

Hi everyone.

George, stephanopolous here.

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