Bakhmut, eastern Ukraine - The city of Bakhmut was home to around 70,000 people before it found itself on the front line of Russian President Vladimir Putin's unprovoked war to seize Ukrainian territory. Almost 12 months of war have left Bakhmut barely recognizable.
Once renowned for sparkling wine, the small city has been reduced to a hollowed-out shell of its former self. But Bakhmut, and the Ukrainian forces defending it, have hung on. "Bakhmut holds" has even become a battle cry for the nation as it fights back against the Russian invaders. But it's only just holding on.
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Even a quick trip to see the central square must be undertaken with one eye on the clock, and the other vigilantly surveilling the sky. The barrage of artillery fire is constant. The sound of shells, incoming and outgoing, fills the air, punctuated by bursts of small arms fire.
The city is absolutely decimated and all but deserted, though CBS News did see a few civilians, astoundingly still trying to eke out a living amid the rubble and ruin.
Seva Kozhemyako, founder and commander of the Ukrainian Armed Forces' Khartia Battalion, and his men are among the forces battling to keep Russia from seizing what little remains of Bakhmut.
It has been one of the most fiercely contested and bloody battles of the war, and as the thunder of artillery continued, Kozhemyako ushered CBS News quickly underground into one of the bunkers from which much of it has been directed.
While the trench warfare along a front line that stretches hundreds of miles from north to south Ukraine looks like something from the battlefields of Europe 100 years ago, Ukraine's fight to hold onto Bakhmut is being waged from high-tech underground command centers.
Inside Kozhemyako's bunker, a small army of volunteer tech warriors - many of them gamers and IT nerds in their pre-war life - carefully monitored screens showing video being live-streamed straight from the front line.
A fleet of inexpensive drones revealed the landscape in astounding detail, from slain Russian soldiers, to fields pockmarked by shells and shattered civilian homes caught up in the battle.
One drone watched recently as Russian troops crawled into a back yard to try to escape a Ukrainian grenade. Often the drones capture images of seemingly helpless Russian forces huddling in trenches before a grenade falls on them. Such clips have spread far and wide on social media in recent months - valuable propaganda for Ukraine and its supporters.
The videos paint a stark picture: Men dying in World War One-style trenches as they come up against 21st-century electronic warfare.
"They monitor the videos, as soon as they see the enemy there, or the tanks, they just start to shoot," Kozhemyako said of the tech team's coordination with troops on the front line.
"We are observing all the movements of the enemy with the help of drones," said Oleksander Pyvenko, commander of the Ukrainian National Guard's 3rd National Brigade.
Pyvenko said the real-time information is used primarily "to support artillery - we see the advances of the enemy and destroy them."
The biggest challenge is detecting Russian incursions before it's too late.
"It can be at night, can be during the day," said Pyvenko, but detecting enemy movements and warning ground forces about them is saving Ukrainian lives.
Gains along the front line just east of Bakhmut, where Russian forces are dug in, have been counted in inches. Russia has thrown wave after wave of soldiers and mercenaries at the fight. Many of them were recently prisoners, lured into the private army of the Kremlin-backed Wagner Group. If they survive, they're promised their freedom.
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Ukrainian forces told CBS News the Russian men are being treated like meat.
Anton Zadorozhyni, battle commander of the Ukrainian National Guard's 3rd Operative Battalion, said that for Russia's forces, there's no option to retreat.
"They are forced to advance over the bodies of their fallen soldiers. One group is destroyed, new ones come… over and over," he said. "At night they collect the bodies."
The Ukrainian forces holding the front line, using the intelligence that comes from tech bunkers, sleep, eat and fight in shifts, right around the clock.
They know that while Russian forces have been killed in staggering numbers trying to take the small city, more will come, and more will die, on both sides.
For the time being, however, from the bunker to the blood-soaked battlefields just a few blocks away, Bakhmut holds.
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