Inside a secret, underground military base in eastern Ukraine

A hidden, underground military base in eastern Ukraine is so secret, soldiers change into civilian clothes whenever they step outside to avoid drawing attention.

Journalists are not usually allowed access.

But the unit that has been using this vast, subterranean warren of war rooms, a dormitory, kitchen, canteen and makeshift gym as its headquarters since the summer is imminently relocating, so Sky News was invited inside.

Lieutenant Colonel Arsen Dmytryc - call sign Lemko - is the chief of staff of 1st Corps Azov of the National Guard of Ukraine, one of the country's most effective combat forces.

He sat with us in the base, next to a large square table, covered by a map of the Donbas region.

His soldiers have been fighting in this area since the summer, countering a surge in Russian attacks in and around the frontline city of Pokrovsk.

"We aim to destroy as much of the enemy as possible," he said.

"Will we take losses? Yes. Will it hurt? Absolutely."

But he said if Russia is allowed to advance, even more Ukrainians will suffer.

"Their [the Russians'] only advantage is numbers," he said.

"They don't care how many people they lose."

Lemko said almost 17,000 Russian soldiers had been killed or wounded fighting in this section of the warzone alone between August to November.

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Ukrainian video footage of the battlefield showed Russian armoured vehicles being taken out by drones and artillery fire.

At one point, Russian soldiers mounted on motorbikes try to advance, only to be stopped by Ukrainian fire.

"Our task is to hit them as hard as possible in various areas," Lemko said. "We focus on our operations, others on theirs, and leadership will negotiate the best possible terms."

The Azov Corps soldiers are fighting over land that should be handed over to Russia, according to an initial draft of a peace deal proposal between Kyiv and Moscow put forward by the United States. This is despite swathes of the Donbas remaining under Ukrainian control.

But General Oleksandr Syrskyi, the head of the Ukrainian armed forces, has since told Sky News that simply surrendering territory would be "unacceptable".

For Lemko, he says the job of his troops is to inflict as much damage as possible on the Russian side to help strengthen Ukraine's hand in negotiations.

"Simply giving it [land] away isn't the way," he said.

"Diplomats do their work, we do ours. Our job as soldiers is to give as many advantages as possible to our negotiating team. And we're doing exactly that."

Lemko, who has been battling against Russia since the Crimean annexation in 2014, also had a warning for the rest of Europe about a rise in hybrid attacks, such as mysterious drone sightings, acts of sabotage and cyber hacks suspected of being linked to Moscow.

He said Ukraine's experience showed that if attacks by Russia that fall under the threshold of conventional war are not successfully countered, full-scale conflict could follow.

"Ukraine once lost a hybrid war that had been waged since the very start of our independence," he said.

"Because of that defeat, there was a physical operation against us in Crimea and then a physical operation in 2022.

"Now the hybrid war has reached its climax, and it is moving into the Baltic States and Europe.

"That is why, in my opinion - and in the opinion of most of our officers - now is the moment for all countries to unite and counter this hybrid war. Because the consequence may be a physical one."

Production: Katy Scholes, security and defence producer, and Azad Safarov, Ukraine producer.

Camera operator: Mostyn Pryce

(c) Sky News 2025: Inside a secret, underground military base in eastern Ukraine