LVIV, Ukraine -- Ukrainian paratrooper Oleksandr Mashonkin suffers from constant headaches and stabbing pains throughout his ribcage. He wakes up at home with a start, imagining himself back in the basement of the state security building in the separatist-held city of Donetsk.
He still can't believe his nightmare is over.
Mashonkin is one of Ukraine's celebrated "cyborgs" -- the handful of soldiers who held out to the end during the brutal battle for Donetsk airport that lasted from September 2014 until January 21, 2015.
Earlier this month, Mashonkin, 29, was released after 197 days as a captive of the self-proclaimed Donetsk People's Republic -- a “Ukrainian slave,” as he says some separatists put it -- in a swap between the Russian-backed rebels and Kyiv.
Mashonkin's unit, the 80th air-mobile brigade, was mobilized on August 13, 2014 -- around the time a rebel offensive that Kyiv says was strongly backed by Russia put government troops under intense pressure. He experienced the hellish fighting in the Donetsk airport buildings, holding out for two weeks against intense shelling and raking gunfire.
On January 21, the roof collapsed in the building that Mashonkin was holding. Ukrainian forces withdrew, and Mashonkin and 14 other "cyborgs" were pulled out -- wounded, but alive -- from the twisted steel and concrete.
Eventually, the pain stopped -- they were beating us so badly that they were just breaking things that were already broken."
The first days of captivity were the worst, Mashonkin says, especially after the "cyborgs" spent a day under the control of the notorious separatist commander Arseny Pavlov, aka Motorola.
"They'd take a few of us away and beat them," Mashonkin tells RFE/RL's Ukrainian Service. "Then they'd bring them back and take away someone else. This lasted all day. They beat everyone -- with pipes, stools, table legs. They beat us all over -- on the head, all over the body, in the groin."
"Eventually, the pain stopped -- they were beating us so badly that they were just breaking things that were already broken."
At one point, Mashonkin says, the men were even beaten by an Orthodox priest.
"When we were with Motorola, a priest appeared -- apparently from the Moscow Patriarchate -- with a cross. He beat us on the head with that cross. Maybe he thought it would drive out our sins," Mashonkin remembers. "He said that we were not human. A priest in a cassock with a cross. And when the wooden cross broke over someone's head, he came back with a metal one. I've seen priests like that only in horror films."
After a day with Motorola's men, the captured "cyborgs" were transferred to a former archive room in the basement of the former Ukrainian security service (SBU) building in Donetsk. For the first time, they were given medical treatment and a change of clothes.
"We were there in the basement without windows for a week or two," he says. "They gave us some kasha or soup twice a day. Later, they put us in another cell with other prisoners."
Conditions in the new cell were better. There were 44 prisoners, but there was a window. Prisoners could listen to the radio.
When they beat us, they tried to convince us to come over to their side. There were Russian mercenaries and Chechens -- who were the cruelest -- and locals from Donetsk."
After a month or so, Ukrainian volunteers tried to see the prisoners and bring them clothes, books, and parcels from their families, but they were not allowed in.
Mashonkin was allowed to telephone his family a couple of times during his captivity from a telephone in the basement of the building.
There was a priest in the cell and the prisoners were allowed to set up a sort of chapel in one corner.
"We gathered there and prayed," Mashonkin remembers. "That made things a little easier."
But the conditions were harsh nonetheless. The beatings continued.
"When they beat us, they tried to convince us to come over to their side," Mashonkin says.
"There were Russian mercenaries and Chechens -- who were the cruelest -- and locals from Donetsk," he says. "We discovered that there were informers among us in the cell, so we learned not to say anything unnecessary."
Shortly after he was captured, Mashonkin was offered the opportunity to participate in a prisoner exchange and gain his freedom. But he says he gave up his place in favor of a fellow prisoner who was more seriously injured. It is a decision he does not regret -- although it meant spending another five months in that cell.
"We were constantly taken out to work," he says. "Cleaning up around town and in the offices of the commanders. They told us we were 'Ukrainian slaves.' When journalists were allowed in, they tried to hide those who had bruises."
At one point, Mashonkin and some other prisoners were taken back to the Donetsk airport and put to work pulling the bodies of their fallen comrades from beneath the rubble.
Back home now, Mashonkin is in the process of demobilizing and finding his way back into civilian life in the western city of Lviv -- far from the Donbas, where the conflict continues despite a cease-fire signed three weeks after his capture.
But he knows the things he endured will always be with him.
"I have always thought for myself," he says. "They tried to break me, to convince me that black was white. It didn't work. But there are still boys back in Donetsk. I got out -- but they are still there."