Defence correspondent
Artem KariakinUntil just over a week ago, Artem Kariakin and his unit were making regular trips across Ukraine's border into the Russian town of Sudzha.
He shows me video taken with a phone of their very last trip, as Ukrainian forces retreated from Russia's Kursk region. It shows them making their way past dozens of burnt out military and civilian vehicles.
A soldier armed with a shotgun, their last line of defence, scans the horizon for Russian drones. Out of nowhere, one flies towards the back of their truck. Sparks fly, but they keep on going.
Artem says they were lucky - the explosive charge was not big enough to stop them.
Another truck nearby was less fortunate. It was already in flames.
Artem admits Ukraine's retreat from Sudzha, the largest town Ukraine held in Kursk, was "not well organised".
"It was pretty chaotic," he tells me. "Many units left in disarray. I think the problem was the order to withdraw came too late."
It wasn't helped, he says, because units were operating without proper communications. The Starlink satellite systems they normally rely on didn't work inside Russia.
The 27-year-old soldier still views the Kursk offensive as broadly successful. Artem says it forced Russia to divert its forces from the east. Most of Ukraine's troops still managed to escape in time – even if for many it was on foot.
But he believes Ukraine's surprise incursion into Russian territory, launched last August, was too deep and too narrow - relying on just one main road for supplies and reinforcements.
While Artem and his men were fleeing for their lives, US President Donald Trump and Russian President Vladimir Putin were talking by phone about trying to bring the war to an end. Artem says he finds that "absurd".
"To me these calls between Trump and Putin are just surreal," he says. "Trump wants to end the war because he promised to do it - and Putin wants to deceive Trump to continue his war. I can't take their conversations seriously."
Artem, whose home is in the now Russian-occupied Luhansk region, tells me he feels disappointed with the US and Trump. "What can I feel when they just want to give away my home?"
Artem KariakinArtem says he never believed that Putin would be willing to trade any part of Russia for Ukraine's occupied territories. But he still believes the Kursk offensive was important to protect its own border. Ukrainian troops may have been forced to retreat, but they still occupy high ground just over the border with Sumy.
Ukraine is continuing its cross-border raids – not just into Kursk, but Belgorod too.
Serhiy's assault battalion helps plan these attacks – finding a way through Russian minefields and anti-tank obstacles known as "dragon's teeth".
We joined him on a night-time mission to locate and recover armoured vehicles in need of repairs. It's the safest time to move close to the Russian border.
Serhiy himself is no stranger to Russia: he was born there. He now has Belorussian citizenship, but he chose to fight for Ukraine. He justifies Ukraine's incursions into his former home. Russia too, he says, has been trying to create a buffer zone inside Ukrainian territory.
Travelling in his Ukrainian-made armoured vehicle, Serhiy still lists the likely threats, now we are less than 10km from the Russian border: glide bombs, rockets and artillery, and drones fitted with thermal imaging cameras.
BBC/Matthew GoddardHis own vehicle is fitted with electronic counter-measures to jam enemy drones, but even those won't work against drones operated via fibre optic wires. Those can't be stopped, though on some routes Ukraine has now erected netting to try to catch the drones before they can hit their target.
Our original search near the Russian border for a damaged US-made Bradley armoured vehicle is abandoned when Serhiy receives intelligence that Russian drones are operating nearby. Instead, he tries to locate another broken-down Bradley where the risks will be smaller.
He and his driver still have to overcome obstacles along the way. Trees and branches lie strewn across their path – remnants from a recent Russian air strike. We see several more explosions in the distance, briefly turning the night sky orange.
Serhiy eventually finds his broken-down Bradley. It's already been retrieved from the battlefield across the border and has been loaded onto a lorry to be taken back for repairs.
The Bradley commander confirms to me that they've been fighting in Russia. He describes the situations across the border as "difficult, but we're holding on".
BBC/Matthew GoddardThe Bradley is another reminder of Ukraine's reliance on US military support. That now seems less certain with Trump's focus on peace talks. Serhiy says it's already clear to him that there's "haggling behind Ukraine's back".
I ask Serhiy if he thinks European nations can fill any void left by the US. Is a European "coalition of the willing" enough to guarantee Ukraine's security?
"I think if America doesn't help Ukraine, then a ceasefire will be agreed soon - but on extremely unfavourable terms for Ukraine," Serhiy replies.
"Europe clearly cannot resolve this conflict alone. They're not strong enough. They've been focussing on their own economies instead of thinking about security."
Serhiy says he wants the war to end. Like many Ukrainians, he would like to see peace - but not at any price.
Additional reporting by Volodymyr Lozkho and Anastasiia Levchenko
