NIU-YORK, Ukraine - The Russian jet cut a path through the tributaries of the Donbas hills, flying low to avoid detection, just as a Ukrainian soldier juggled three unruly kittens in his meaty palms.

It was half of a litter, explained the soldier, who goes by the call sign Yarik, as their mother prowled the edge of a dugout. Within minutes, the enemy Su-25 fired a missile, striking a position about 300 meters away with a thunderous crack.

"Bunker! Bunker! Bunker!" the soldiers shouted, sending humans and felines alike seeking cover in the shadowy earthen shelter with a pine log roof. After a few minutes with no follow-on attacks heard, the men, from Ukraine's 24th Separate Mechanized Brigade, filtered back to the edge of the trench line, where younger troops instructed an older soldier how to use a vape pen. He asked about the flavor he was struggling to identify.

"Peach!" One soldier yelled out, laughing. "Or no, mango!"

Their position, outside the town of Niu-York in Ukraine's eastern Donetsk region, is among a string of machine gun nests and observation posts that loosely form what commanders say is a rarity: a front-line that has more or less stayed the same since 2014, when Russian forces and their separatist proxies first fomented war in Donbas and began seizing territory. Russian positions are about 400 to 500 meters away, well within machine gun and sniper range.

The nine-year-long status quo near Niu-York may soon be challenged by battles in Bakhmut to the northeast and Avdiivka to the southwest, where Russian troops are making bloody gains. A breakout in those areas, leaders have said, would strangle supply routes into the area and risk units here becoming encircled.

In this grinding war, with advances made in feet, not miles, the joining of Russian troops, from north and south, into a unified westward-pushing line of attack would be a major triumph, and would further President Vladimir Putin's goal of seizing all of Donetsk region, as well as three others: Luhansk; Zaporizhzhia; and Kherson.

The terrain near Niu-York itself is a formidable obstacle that the Russian forces use to their advantage, soldiers said. The rolling hills provide ample cover for enemy troops to maneuver without being seen until they attack in small groups, probing the lines for weaknesses or trying to provoke Ukrainian troops into firing and revealing their positions.

Ukrainian forces occupy the high ground in some areas but are in lower elevation bowls in others, a tactically dangerous scenario, in which enemy troops can look down to rain gunfire and have an expansive view to call in artillery strikes. The Russian forces have operated here for years and know the terrain well.

"The landscape is not completely in our advantage. We don't always have the best positions. We don't always see them," said a senior sergeant who gave only his call sign, Grek, to adhere to Ukrainian military rules. The soldiers used the same strategy as the Su-25 pilot, he said, who harnessed the topography to cloak their position between two hills until they released munitions from a few miles away. The plane evaded radar and was not detected until it fired and returned home, Grek said.

The spring thaw will bring a much-needed reprieve from the harsh freezing conditions that make trench warfare insufferable, but it will also complicate matters. Some hilly positions have perhaps 65 to 100 feet of visibility through leafless trees, but foliage will soon limit the view, Grek said.

While fighting in this area has quieted in recent weeks, the region remains an important buffer to keep Russian forces, currently split, from combining along the front.

"The longer we hold this line, it also means it'll be better and easier for Bakhmut," Grek said, stopping intermittently to click his radio and answer soldiers checking in from their positions. "Well, not easier. I can't say that about that place. But if we pull more enemy forces into this direction, it might calm down the situation for the guys there, and maybe stop a full encirclement."

The town of Niu-York, free from skyscrapers but speckled with occasional references to its American namesake, has endured shelling and destruction for as long as any other front-line town since 2014. Townspeople who have not yet evacuated shuffle past blocks of pulverized homes and boarded-up schools, and the occasional tractor tills black soil in anticipation of spring.

A woman feeding dogs and cats on one block and who gave only her first name, Yevhenia, said she did not want to talk about anything except the animals. Some pets were abandoned by people who fled, she said, and others wandered into town recently. She was trying to nurse Cutie, an affectionate gray and brown cat showing signs of infection, back to health.

Beaming with pride, Yevhenia, 69, said she took part in helping spirit 35 dogs to a shelter in Dnipro, part of a long history of looking out for animals. "I have been doing this for my entire life," she said.

Back at the position, the soldiers said the shelling and firefights were not as intense as previous areas where they were stationed, describing this chunk of the front as a place of relative quiet.

Several mentioned they had been wounded in other engagements. A 56-year old soldier who used to work as a customs officer (call sign: Customs), said an explosion north of Bakhmut broke five of his ribs, peppered his leg with shrapnel and left him with a concussion.

Recovered now, he shouldered a U.S.-made M240 machine gun and fired two bursts across no man's land. The lines are close enough to see enemy soldiers, but he wasn't sure he hit any of them. No matter. "It feels so euphoric," he said, to fire the gun.

Other epiphanies have spread throughout the position. A 19-year old soldier, nicknamed Little One for his youthful face and slight build, said he put his amateur mixed martial arts fighting career on hold to enlist soon after the Russian invasion last year. Now, he is assigned a DShK heavy machine gun probably bigger than he is, with no plans to return to civilian life even if the war ended tomorrow. "It's a brotherhood, one big family," he said.

The security of the line depends on a symphony of specialties, from infantry braving the trenches to artillerymen firing on enemy positions, supported by drone pilots who help them adjust their targets.

Others hunt armored vehicles and tanks, including a four-man team that describes itself as "ninjas in the bushes" that assembles and fires their Skif, a Ukrainian guided-missile system, whenever they are dispatched for an assignment. The team - commander Dmytro and soldiers with call signs Viper, Joker and Artist - have videos on their phones showing the Skif blowing up vehicles. Some were occupied, they said, others weren't. Some they didn't know.

The job has provided a front-row seat to some of the most peculiar behavior on the Russian side, Viper said, recalling one moment where he watched a group of three soldiers dig a position. He fired an antitank gun, killing them on the spot. Another group came out to dig. He fired again and again - all day, he said, adding: "I helped them dig that hole."

The enemy are digging and building all over the place, it seems. Digging trench lines. Building antitank defenses. The drones are capturing all that activity, Grek said.

His soldiers are mentally exhausted in this grinding phase, he said, but preparing for more fights to come.

"We will have to push this front further and further back. That's not up for discussion, that's how it has to be," he said. "Our brigade commander told us the same thing: 'Boys, while we're here, we're resting, but there will come a time where the command will come to boldly move forward.'"

Grek said that he had an aversion to guns and firearms before the war. As soldiers filed past him carrying Kalashnikovs, he said he still does not want to use them. "We'll have to ask them to leave," he said of the enemy. "Or force them, I guess. That might be easier."