Back in May, the Biden administration started giving Ukraine the green light to strike over the border into Russia using US weapons, provided it was for self-defense. Now, this was a big deal because previously, it was only allowed to use those weapons in areas within Ukraine that Russia had already occupied.

An angry Putin saying NATO risks a full-on war with Russia, but that Moscow also give arms to US adversaries around the world.

Ukrainian soldiers told CNN they noticed a difference, that those strikes slowed the Russians down before they even crossed into Ukraine. However, it's one thing to send rockets into Russia, but a full-on ground incursion, that option didn't seem to be on the table. Well, until recently, that is. My guest is Daria Tarasova-Markina. She's a Ukrainian Indian journalist who has been working hand in hand with our CNN teams on the ground. We spoke on Thursday. Today, the story of how a surprise dash across the border caught the Russians off guard and how it could change the course of the entire war. From CNN, This is One Thing. I'm David Reind. So, Daria, where are you right now?

So right now, I'm north of Ukraine. It's suma region because right now, as probably for sure you know, that Kursk mission is going on. I'm here with the CNN team covering the story. This is not far away from Russian border where the story is going on right now.

Right. The Kursk region, this is where this whole incursion is happening. But can you tell me, how did it start?

Yeah, it's a very interesting story. Everything started on August sixth. There was something, something happened. We saw some statements from Russian Security Service. They said that it was some provocation on the border. Okay, it's not the first time, provocation on the border. Then we found that some statement from Russian MoD, Ministry of Defense.

According to Russian officials, this is indeed the Ukrainian regular military launching now for two days an incursion across the border into Russia, near a town called Suzhja.

And then there were more and more and more information, but Ukraine said nothing, like nothing from authorities. And then We started seeing videos from soldiers who were coming to the territory, and there were a big number of Ukrainian troops on the Russian territory.

Ukrainian troops appear to have captured an important natural gas hub in Russia's Kursk region. Video of them standing in front of the facility was posted on unofficial Telegram channels. Cnn has ge-located this footage from the Kursk region, which shows burnt-out Russian military trucks and the bodies of military personnel.

We started calling authorities, Ukrainian authorities, asking what's going on, and no one said nothing. It was just silence. Then there were more and more and more and more video on social media. We understood that, Okay, this is serious.

Ukrainian troops sweeping through Russian territory. Dear Ukrainians, this soldier starts and then says his forces went into a Russian supermarket, but that Ukrainian stores have a better selection. And eventually, in a few days, Ukrainian authorities said that, Yes, this is the mission.

We keep going. We are coming there, and we are just taking one village, the second village. And we saw all of these Russian prisoners that were taken as POWs. We saw all of that battles. And now we are here. It's more than one week, and now There are more than 70 settlements, I think.

President Zelenskyy says in the last 24 hours, Ukrainian forces have seized another 15 square miles of Russian land in the Kursk region. That brings the total of the week-long surprising Kursh into nearly 400 square miles. To put that into perspective, that's as much ground as Russia has gained in Ukraine over the last year.

And can you put into perspective just how big a deal it is for the Ukrainians to go across the border like they did? Because they had been firing rockets, but this was actually going to take villages, right?

Yeah, exactly. I mean, we have troops on the ground. There are Ukrainian soldiers who are already in that territory. It's not just sending drones or missiles. It's just like taking POWs. It's coming to this abandoned Russian positions.

Now, this is what's so startling about this offensive, the volume of Western-supplied armor that we're seeing passing back and forth.

So today we were near the border. The border itself is destroyed. We were on Ukrainian side, so we did not cross the border yet. But still, just to see this huge destruction everywhere to see this Russian signs on the border that was destroyed.

It's also remarkable. The freedom with which the Ukrainian military are moving around here, they simply aren't afraid of the drones that have hampered their every move for the past months.

We saw a lot of vehicles that were going in, going out, and Ukrainian soldiers that were there, and they seemed quite relaxed. They were just like... You did not feel that it was very nervous, very active.

It seemed like they were in control of the situation.

Yes, exactly. You're totally right. We are in touch with several soldiers who are already there, and they are doing this mission. They are moving forward. No one knows the final strategy. No one talks about the final goal. We asked authorities. We asked just ordinary soldiers. Just today, the soldier told us, I'm just doing my task. I have to ask, and I'm doing it right now. So it seems that no one talks about the strategy. No one talks about it. Where are you going? What's final goal of this?

Right. I mean, that's what I was going to ask. How far do they want to go? Is this just to punch Russia in the nose, or is there some greater objective at play here?

It's quite difficult to say it because probably only Ukrainian authorities and military generals know it. It could be probably to do a buffer zone to protect Tsume because I visited yesterday the shelter where the people are coming from regions that are very, very close to the border. And those people told me that previously, Russian soldiers used artillery. Now, they can't do it because they were moved.

So because Ukraine has moved past the border into Russia, there's a zone, and Russia can't fire right into these villages right along the border, you're saying?

Exactly. Yes, this is what this residence told me. But now, Russian soldiers, they are using cops. This is aerial guided bombs, which is hugely devastating. But still, it's not so many artillery. There are not so many drones. So it could be the one reason. The other one reason, maybe this is something for the morale, because I can tell you that the morale among soldiers is super high. One commander with whom I talked to yesterday, he told me that dreams come true. He meant that we have been fighting here. I mean, they have been fighting here in Ukraine for years. And his message was, if Russians came to Ukrainian land to fight, so that means that this war can come back to their land. He told me, They attack, we attack. And for them, their morale is just super high. You can feel it in the air.

Well, so how has Russia been dealing with this? Because they seem to have been totally caught off guard by this.

Yeah. So you could see that there are a lot of POWs They are soldiers. They're not fighting. And again, that commander whom I talked to yesterday, he told me, It's so interesting. It seems that Russian soldiers, they are ready to die for Ukrainian land, but they are not ready to die for their own land. The Russians are now trying to stop our advance.

They have pulled in reserves, which has benefited our defense forces in other areas because it's become easier to work there. From what I was told also about some military guys that Russia trying to protect their land, they move their soldiers from Crimea, from Zaporizhya, from Kharkiv direction, and they see that Russians are moving their troops from different directions. So they're diverting troops from Ukraine into Russia to go deal with this?

Yeah, of course. They have to do something, and they need people for this. So, yeah, they just move their troops from other battlefields.

What has the reaction been from the US and the international community? Because it is honestly reminiscent of what Russia did to them two years ago. Obviously, that was completely unprovoked on the part of Russia. But are there any concerns about an escalation like this?

Well, of course, you have seen that the statements were quite accurate here, that most countries supported Ukraine's right to self-defense. Again, Ukrainian authorities are very careful with the statements. But again, coming back, we talked about morale among soldiers. You know what I was surprised to see in this evacuation center here in Ukraine? Normally, when you come to such places, you feel a high level of desperation. Because people had to leave their houses. They don't know whether they can come back to their places and so on.. Here in summer region, when I came to this evacuation center, I found that people were scary, obviously, but still they supported Ukrainian army, and this level of hope you could feel it.. I I mean, it was higher than level of fear, and it was interesting. So maybe this one of the targets, one of the goals, I mean, I don't know. Let's see.

You're a native Ukrainian, right? This is your home.

Yeah.

So what has it been like reporting on this war for the last two plus years?

You know, I was thinking, who am I? Am I a journalist or am I Ukrainian? But obviously, of course, it's difficult because every time you're trying to stay objective, you are trying not to be too emotional. You're just trying to tell the facts. But at the very end of the day, of course, it's your country, it's your people. You have more feelings than just covering the story. But once a CNN producer once gave me a very good advice. He told me, Hey, listen, bad is bad, good is good. When you're on the ground, just think about it, not about who you are, where are you from. Just when you're telling the stories, try to understand whether it's good or bad. I'm just trying to tell the stories, trying to show what's going on here, trying to show people's stories, because at the very end of the day, I think that story really matters. This is something that connects all of us all around the world. And just to help people who are living very, very far away to understand what's going on here or there. Yeah, of course, it's difficult to cover the world when There is the war in your country.

But we try to do our best.

Well, thank you so much for bringing us these stories. I really appreciate it, Dharia. Thank you.

Thank you. Thank you, David.

One Thing is a production of CNN Audio. This episode was produced by Paulo Ortiz and me, David Reind. Our senior producers are Felicia Patinkin and Fez Jamil. Matt Dempsey is our production manager. Dan Dizula is our technical director, and Steve Ligtai is the executive producer of CNN Audio. We support from Haley Thomas, Alex Manasari, Robert Mathers, John Dianora, Lanie Steinhart, James Andres, Nicole Pessereau, and Lisa Namarau. Special thanks to Goldis, Victoria Butenco, Ivana Khodasova, Wendy Brundage, and Katie Hinman. We'll be back on Wednesday with an episode from the Democratic National Convention in Chicago. Big political week ahead, so head over to cnen. Com or the CNN Five Things podcast for all the updates. In the meantime, I'll talk to you later.