BBCFor the previous 72 hours, the menacing whirr above our heads has belonged to Russia’s suicide drones, passing over and then bearing down on their targets.
Now the buzz comes from a Ukrainian unmanned aircraft which has not been sent up to kill, but to relay footage from the training ground to commanders back at base.
We’ve been brought to a secret training location in the Chernihiv region where the latest army intake is being fast tracked to the battlefield in the renewed effort to blunt Moscow’s grinding advance.
In the hail of machine gun fire and instructors’ commands, the most striking aspect of the scene is the age of the new recruits. Most seem to be in their 40s and 50s.
Among the grey-haired contingent, Rostyslav, whose wife and two children are waiting for him back home in the Odesa region.
A month ago he was a driver. Next month he could find himself fighting on Russian soil, with Ukraine vowing to hold on to the land it seized in the Kursk region during its lighting incursion a month ago.
“I think this is the right thing to do,” he says of the operation.
“Look how long they’ve been on our land. We’ve been suffering for so long, we have to do something. You can’t just sit there while they are capturing our territory. What will we do then? Will we become their slaves?”
The training schedule we’re witnessing reflects the accelerated programme new army joiners are undergoing as Ukraine tries to deal with the sheer mass of men Russia is committing to the frontline.
The Ministry of Defence in London estimated there were 70,000 Russian casualties in Ukraine in May and June alone.
Under the scorching sun, the new Ukrainian recruits jump in and out of American-made armoured fighting vehicles and open fire on enemy positions.
The military, anxious that the location of this training remains secret, asked to see the footage we recorded on location before this story was reported across BBC News – but did not see any scripts nor have any editorial control.
In a nearby woodland, a simulated Russian attack on Ukrainian trenches is repelled while the boom of grenade target practice shudders across the plain.
Two and a half years into the war, and Ukraine is desperate for more troops and brought into force a new conscription law which lowered the age of men joining from 27 to 25. Military service for women is not mandatory.
The drive for younger conscripts has not hit this group of men.
All the recruits we see before us have already had 30 days of basic training and today it’s more advanced care – dealing with broken bones, gunshots and catastrophic bleeding – using medical equipment sent from the UK.
Light-hearted moments – a decidedly wonky tourniquet here or there – punctuate a heavy air.
There’s no escaping the fact the simulated emergency care being given under shade of spruces could be carried out in grim reality in the coming weeks and months.
One soldier who’s accompanied us to the site says that if the new intake have not acquired enough fighting skills they will not be sent to the frontline.
“We’re not going to send them to their deaths,” he says sharply.
Still, we have heard complaints, notably from professional soldiers, that raw recruits have been sent to other fronts without inadequate training and thrust prematurely into frontline combat.
Ukraine is on the back foot in key parts of the battlefield at home, most notably around the strategically important city of Pokrovsk in Donetsk.
But last month’s incursion into Russia has boosted morale and has added a new dimension to the war.
However, Kyiv is now fighting a battle on yet another front and this is a huge personal gamble for President Zelensky.
His generals have tough strategic decisions to make about where to send their new recruits.
Maxim, a 30-year-old builder by trade, looks to be the most youthful of the cohort.
“We need to train, train and train again. The more we train the more we will learn here. It will help us on the frontline.”
Where will that be, I ask? “We are ready to defend our land either in Donbas – or Kursk,” he says proudly but with a nervous laugh.
ReutersEarlier, in Ukraine’s Sumy region, we had travelled under military escort to a new Ukrainian base just a few miles away from the Russian border.
Along the way, we passed whole streets blasted to pieces by previous Russian artillery fire.
The civilians had long gone, and the only human life was clad in the green and driving army vehicles.
As we arrive at the camp, an armoured personnel carrier (APC) fresh from the Kursk incursion roars into life and springs up backwards out of its sunken hiding place.
It pivots and then speeds off through the canopy lined track, leaving a huge plume of copper-coloured dust.
“The Russian soldiers who surrendered, we took as prisoners of war. The Russians who attacked us, we killed.”
It’s a blunt synopsis from the Ukrainian commander who goes by the call-sign “Storm”.
His 22nd Mechanised Brigade was the first to enter Russian territory and now he’s returned to tell the tale.
“We went far into the Kursk region. We were alone as the forward team. We were on foreign soil and we felt like foreigners. Not in our home.”
A father of five with five degrees, Storm cuts a distinctive shadow in the dense forest.
A giant of a man with greying goatee and military tattoos on the skin not covered by his army fatigues and body armour.
“That’s us, in there,” he says showing us a video on his phone of an APC tearing through the Russian countryside.
What was it like fighting the Russians on their home soil, I ask?
“I worried for myself and for my group, for my servicemen, for everyone. Of course, there was fear. “
Like all of the Ukrainian military me met, Storm is understandably reluctant to give any operational information which may help the Russians.
So when I ask if he knows how long he’ll stay on Russian territory when he returns, it is an answer predictably long on patriotism and short on specifics.
“We are fulfilling an order. We’ll be there as long as we are told to. If we are told to move forward, we will move forward. If they tell us to withdraw, we will withdraw.”
He continues in the same vein: “If we have an order to move forward, we can get to Moscow – and we’ll show what Ukraine means and what are our guys are like – real Cossacks.”
It’s been reported that Ukraine sent up to 10,000 elite troops into Russia as part of its rapid advance.
The Russian defence ministry claims Kyiv has suffered thousands of casualties.
The head of the Ukrainian army, Gen Oleksandr Syrskyi, announced the Russians had now sent 30,000 troops to defend Kursk. All these figures are hard to verify.
In another clandestine location, a team clambers out of a German-made Bergepanzer armoured recovery vehicle.
The driver, who goes by the call sign “Producer”, is a father of two who hasn’t seen his two children for three years.
They escaped to Italy with their mother in the weeks after Russia’s full-scale invasion in February 2022.
While we’re unable to ascertain the level of Ukrainian losses, it’s clear that Producer has been busy bringing back damaged and destroyed vehicles from inside Russia.
“I want this war to come to an end,” he tells us wearily in very good English.
“That’s because there is no reason for this (war). One man, Vladimir Putin, attacked our country. So what do we have to do? We must defend our home. Defending, defending, defending. But Ukraine is the smaller country.”
The mismatch between Moscow and Kyiv remains a key thread of President Zelensky’s ongoing call for greater Western help.
Through taking the fight into Russia, Ukraine galvanised its public but worried some allies who remain fearful of Vladimir Putin’s response and the spectre of a wider conflict.
So far, President Putin has largely ignored, at least publicly, the wound inflicted on his country’s side.
Ukraine says that, unlike Russia, it doesn’t have unlimited reserves of conscripts to catapult to the frontline.
We saw a glimpse of the deployment dilemma with our own eyes in the locations we visited this past week.
President Zelensky argues that much greater American and European assistance in air defence is more vital than ever and that permission to use foreign-made long range missiles to strike further into Russia urgently needs to be granted.
Especially now that Kyiv is fighting a battle at home and abroad.
As we leave the training ground, the exhausted soldiers loll on the ground – water bottle and cigarette in hand for many.
Rostyslav, who longs to return to his Odesa, believes his president is absolutely right.
“The Russians can reach our territory with long range weapons and we don’t have such a weapon to reach their territory. We can’t stand this anymore” he explains.
“We would like to hit Moscow to end this dirty war. Children and civilians suffer, everyone does.”
Another rocket-propelled grenade thunders across the parched training field.
Next time, it won’t be a drill.
Additional reporting by Kyla Herrmannsen, Anastaciia Levchenko
