They were captured by the Russians. Then the hardest fight began.

Shot through the jaw and tongue by a sniper round last year during the final days of the heavy siege of the Azovstal steel mill in Ukraine, senior Sgt. Maksym Kushnir could not eat or speak and could barely breathe.

But when he stumbled out of a bunker last May with hundreds of other wounded Ukrainian soldiers in a negotiated surrender with Russian troops, there was no medical help or any sign of the Red Cross workers they had been promised.

Instead, Sergeant Kushnir, a soldier of nine years and a poet since childhood, said he was taken on a two-day bus trip into Russian-controlled territory and left to die on a bed, jaw shattered and gangrene spread across his tongue.

“I thought this was the end,” he said. “They did nothing for the first three to four days. They expected me to die alone.”

That Sergeant Kushnir survived and returned home to tell the story is one of the success stories of the war. Even as the two sides are embroiled in a full-scale conflict, Ukrainian and Russian officials have exchanged hundreds of POWs on an almost weekly basis.

But the prisoner exchanges have also revealed a grim reality. Ukrainian soldiers have come home with stories of terrible suffering in Russian captivity executions and deathsbeatings and electric shocks, a lack of health care and near starvation rations.

Ukraine gives the International Committee of the Red Cross access to the Russian prisoners of war it holds, an indication that it is fulfilling its obligations under international treaties of war. Russia does not. It limits outside surveillance and has confirmed the identities of only some of those it detains.

Ukrainian officials and former prisoners say the Ukrainian prisoners were visibly worse off than Russian prisoners on exchanges.

“We were so thin,” Sergeant Kushnir said, holding up his little finger. “Compared to us, they looked good. We were skinny and bearded. They were shaved and washed.”

“It’s a classic abusive relationship,” said Oleksandra Romantsova of the Center for Civil Liberties, a Ukrainian organization that received the Nobel Peace Prize last year, listing the treatment of Ukrainian prisoners.

It is unclear how many Ukrainian soldiers are prisoners of war or missing. Russia has provided only partial lists of those it holds, and Ukraine is not disclosing figures. But human rights groups say there are at least 8,000 to 10,000 detainees, and Ukrainian officials have not disputed those figures.

And more Ukrainians have been drawn into the fighting in and around the city of Bakhmut in recent months, according to people working to bring prisoners home. It is believed that there are far fewer Russians being held by Ukraine.

Some Ukrainian soldiers have also been tried in Russia on dubious charges and received long sentences in Russia’s penal system, said Oleksandr Pavlichenko of Ukraine’s Helsinki Human Rights Union.

Five hundred medical personnel and hundreds of female soldiers and wounded are among the prisoners of war, said Andriy Kryvtsov, the chairman of the Military Medici of Ukraine. He said 61 military medics remained in captivity and called for their release.

Dr. Yurik Mkrtchyan, 32, an anesthesiologist, was one of more than 2,000 captured after fighting at the Ilyich steel mill in Mariupol last April, many of them wounded soldiers he tended to.

He said the Russians provided medical assistance only when he begged them and did not take the wounded to a hospital until they were near death.

Dr. Mkrtchyan, who was released after a prisoner exchange in November, said he remained concerned about the condition of the injured, including amputees.

“It was just the guys protecting our hospital,” he said. “Most of them are still in captivity and I see no excuse or explanation for that because they are already disabled, they can’t fight, there is no reason to keep them in prison.”

Former prisoners and human rights groups say Ukrainian prisoners, including the wounded and pregnant female soldiers, have been brutally mistreated.

Dr. Mkrtchyan described how newcomers had to lead a cartel of prison guards who beat them with sticks, a hazing ritual known as a “reception.” He recalled running head down through the torrent of blows and seeing a fellow prisoner lying on the floor. The soldier, a wounded inmate with severe burns named Casper, was killed by the beating, he said.

Maksym Kolesnikov, 45, was one of more than 70 Ukrainian soldiers and four civilians captured in the days just after the Russian invasion in February 2022, when Russian troops captured his base near the town of Hostomel, north of Kyiv, the capital of Ukraine. Ukraine invaded.

The men were taken to a filtration camp in a disused factory for interrogation, where their commanding officer was beaten within earshot of the entire unit. Russia’s network of filter camps, where military and civilian Ukrainians are screened and interrogated, has been widely criticized for human rights violations.

After a few days, Mr. Kolesnikov and his fellow prisoners were transferred to a Russian prison in the Bryansk region, near the border with Ukraine.

The beating of the “reception” lasted five hours. “I got a knee in the face,” he said. The beatings continued daily for a month. The guards used rubber batons, plastic pipes, wooden rulers and knotted lengths of rope, or simply kicked prisoners, he said.

Prisoners nicknamed a group of guards “the Electricians” because they tormented prisoners with electric shocks.

The prisoners were dangerously malnourished, Mr Kryvtsov said.

“It was a good day when you found a potato in your soup,” said Mr. Kolesnikov, who added that he had lost about 75 pounds in captivity.

He said he suffers from a compressed spine from malnutrition and hip and knee injuries from the prolonged blows.

Oleh Mudrak, 35, the commander of the First Azov Battalion, was unrecognizable and painfully thin when he returned from four months of captivity after being captured at the Azovstal factory in Mariupol, his cousin Danylo Mudrak said.

He put on weight and underwent surgery on his shoulder, but died of a heart attack five months after his release, Danylo Mudrak said.

Members of the Azov battalions, long portrayed by Russia as neo-Nazis as part of its justification for the war, received particularly harsh treatment, according to Major Dmytro Andriushchenko, who was deputy commander of the Second Azov Battalion when he was killed. captured in Azovstal. “Azov was like a red rag to them,” he said.

Major Andriushchenko was in a penal colony in Olenivka in July when an explosion ripped through a barracks, killing at least 50 Azov members. Like several former Olenivka prisoners who were interviewed, he accused Russia of orchestrating the explosion.

The prison guards closed the gates to the barracks to prevent survivors from escaping, Major Andriushchenko said.

Dr. Mkrtchyan, who was in the same penal colony, said he and other Ukrainian medics urged the guards to let them help the wounded, but were not allowed to leave their building.

Russia has blocked calls for an independent investigation in the explosion and blames it on a Ukrainian attack.

For some of the injured from Azovstal, visits from Russian television crews may have been a life saver. The publicity put pressure on Russian authorities to care for the prisoners, who were already frail from their besieged time in Azovstal with little food and water, Sergeant Kushnir said.

With his jaw broken and gangrenous tongue, Sergeant Kushnir could not lie down and sat with his head in his arms for days without any painkillers or antibiotics.

He was eventually transferred to another hospital where doctors amputated his tongue and closed his jaw.

He dreamed of food. He wrote a verse:

“Have mercy on me, fate. I’m alive.

Do not punish me mercilessly.”

The physical pain wasn’t as hard to bear as the uncertainty of captivity, he said.

“If you don’t know what to prepare for, what the next day will bring,” he said, “especially after you’ve seen what the Russians did to our men and you were constantly waiting for death, it’s not a cool feeling. not at all.”

At the end of June, Sergeant Kushnir and other wounded men from Azovstal were loaded into buses and driven to the front line to be exchanged.

Back in Ukraine, he underwent multiple surgeries and spent months learning to talk again by exercising the scar tissue in the back of his throat.

His surgeon, Dr. Vasyl Rybak, 44, the chief of the department of rehabilitation and reconstructive surgery at an Odessa hospital, took bone from his hip to reconstruct his jaw, but when that didn’t work, he put in a titanium jaw, created in a 3D printing lab in the city of Dnipro.

Subsequently Dr. Rybak plans to learn from pioneers in India how to make a new tongue for his patient from muscle tissue in his chest.

“He’s a hero,” he said of Sergeant Kushnir during a post-surgery pause. “They all are.”

Oleksandr Chubko And Dyma Shapoval reporting contributed.