VOLYN REGION, Ukraine — In a thick pine forest in western Ukraine, not far from the border with the Kremlin-aligned nation of Belarus, a military engineer named Anton is supervising a vast underground construction site.
"It's a bunker," says Anton, who, like the other soldiers in this story, declined to give his last name for security reasons. "We shipped in most of the wood because we didn't want to cut the trees here. We need them for cover."
He won't say how many soldiers the bunker, which is almost finished, will house. But he does give NPR a tour, walking us through a labyrinth of small hallways connecting bedrooms, bathrooms, a kitchen and dining hall, and a large central command room lined with desks and giant TV screens.
"All these videos are from the borders," says Stanislav, a 34-year-old computer scientist who is the tech support here. "If something will start, we will see it."
Russian troops entered Ukraine through Belarus in the beginning of the war, before retreating after a failed attempt to occupy Ukraine's capital, Kyiv. Since then, the border has been largely quiet, though Ukrainian authorities sometimes warn of brewing Russian offensive here. Ukrainian authorities say about 10,000 Russian troops are still in Belarus, only about 10% of the number before the Russian invasion.
But with Russian President Vladimir Putin signaling a long war ahead, Ukraine is fortifying even the quietest stretch of its border with Belarus.
"In this war," Anton says, "we can't take any chances."
On the Belarus frontier: trees, mud and swamps
The forested terrain in the northwestern Volyn district makes it difficult for tanks to cross the border. This year's unusually mild winter, as well as dams built by the local beaver population, have also made the border area especially muddy and swampy.
But that doesn't mean infantry and saboteurs can't cross on foot, says Oleksii, the gravelly voiced, middle-aged commander of a small unit deployed here.
"We walk along the border every day and watch what's happening in real time," he says. "We catch what the cameras may miss."
A gray-haired soldier using the call sign Sturman says he noticed something troubling on the Belarusian side of the border during one of his recent patrols: men in military clothes digging trenches and fortifications.
"I saw them with my own eyes," he says.
Sturman says his unit recently blew up a road leading to the border because it looked like tanks could cross there. Other parts of the border are mined.
"This war will probably last a long time," Oleksii says. "Even the safest places are not safe."
With the border calm, it's time to train
Ukraine is using this region, quiet for the moment, to train troops for the front line in the east.
Further from the border, in muddy fields past the forests, the soldiers teach each other how to use heavy artillery, including a howitzer, a large artillery piece something between a cannon and a mortar.
Vadim, a banker-turned-soldier who is among the troops training here, doesn't bother covering his ears from the explosions.
"I hope Lukashenko heard that," he says, referring to Aleksandr Lukashenko, the Kremlin-aligned autocratic president of Belarus. "Just in case he thinks we're just sitting here drinking coffee all day."
Lukashenko recently visited China's president Xi Jinping in Beijing. Xi is expected in Moscow this week. The prospect of China assisting Russia and Belarus unsettles Vadim.
"And yet, it also doesn't matter," Vadim says. "We have no choice. We will still fight."
He's wiping down some of the shells, which are rusty after being in storage for years. He takes out a marker and writes a message on one of them: "Biden, thank you for the weapons, we need more."
"If we get F-16 [jet fighters], maybe we could even win this year," he says.
"Well, most of the tanks haven't even come in," says Alex, another soldier, referring to the M1 Abrams and Leopard 2 battle tanks promised by the U.S. and European nations. "So...fight with what you have."
He sees northwestern Ukraine as "not just a training ground, it's also a support hub."
"Our military can regroup here, get new equipment, new ammunition," he says. "That's why we have to protect it. Because if the Russians cut this line of support, our guys in Donbas can't get supplies or reinforcements."
The soldiers training here will deploy to Donbas. Alex is a bomb specialist who worked security in Afghanistan. But other soldiers aren't as experienced.
Volunteers have cast aside their civilian lives and headed to war
"Before the war, I was the dad who wore a suit and tie and went to work in a bank," says Vadim.
Then, the day after Russia's full-scale invasion on February 24 last year, he enlisted. A few days after that, Vadim was fighting Russian soldiers trying to take over Kyiv.
"This is now my job," he says. "Keeping Russian soldiers out of Ukraine."
Ukraine's military relies on volunteer units to supplement the professional army. Vadim is training with carpenters, plumbers and accountants. Some men are older than the typical soldier – one is a grandfather of four.
Several soldiers in their battalion just left for Bakhmut, the ravaged city in the east where the longest and bloodiest battle of the war is taking place.
Russian forces, including mercenaries of the Wagner Group, a private army funded by a Russian oligarch, have occupied part of the city. Ukrainian forces are struggling to keep them back.
"The Russians may never come [to Volyn]," Alex says, "so we will go to them."
The soldiers fry potatoes and ham on an open fire for lunch. They raise hot mugs of instant coffee to their colleagues who have deployed out east. Then they return to the howitzers, knowing they don't have time to waste.
NPR researchers Zazil Davis-Vasquez and Barclay Walsh contributed to this report.
