Servicemen of the Carpathian Sich Battalion are seen on a tank on a frontline, as Russia's attack on Ukraine continues, near the town of Lyman, Donetsk region, Ukraine December 8, 2022. REUTERS/Viacheslav Ratynskyi 

A tear is seen on the face of a Ukrainian serviceman, amid Russia's attack on Ukraine, on a frontline in Donetsk region, Ukraine November 30, 2022. Radio Free Europe/Radio Liberty/Serhii Nuzhnenko via REUTERS 

Petro, 35, a member of the 68th Independent Jager Brigade of the Ukrainian Army sits for a portrait in the sleeping quarters for him and other members of his brigade in a dug out field position near the frontline in the Southern Donbas region in Ukraine, November 29, 2022. REUTERS/Leah Millis 

A serviceman of the Carpathian Sich Battalion is seen at his position on a frontline, as Russia's attack on Ukraine continues, near the town of Lyman, Donetsk region, Ukraine December 8, 2022. REUTERS/Viacheslav Ratynskyi 

A serviceman of the Carpathian Sich Battalion rests at his position on a frontline, as Russia's attack on Ukraine continues, near the town of Lyman, Donetsk region, Ukraine December 8, 2022. REUTERS/Viacheslav Ratynskyi 

A member of the 68th Independent Jager Brigade of the Ukrainian Army scans the horizon for Russian military from his position in the trenches near the frontline in the Southern Donbas region in Ukraine, November 29, 2022. REUTERS/Leah Millis TPX IMAGES OF THE DAY 

Servicemen of the Carpathian Sich Battalion are seen at their positions on a frontline, as Russia's attack on Ukraine continues, near the town of Lyman, Donetsk region, Ukraine December 8, 2022. REUTERS/Viacheslav Ratynskyi 

Viktor, 56, a member of the 68th Independent Jager Brigade of the Ukrainian Army drinks hot coffee in the kitchen area in a dug out field position near the frontline in the Southern Donbas region in Ukraine, November 29, 2022. REUTERS/Leah Millis 

Ukrainian servicewoman Valeriia, 28, holds one of two puppies found two weeks ago in an abandoned house in a frontline, amid Russia's attack on Ukraine, near the town of Bakhmut, Donetsk region, Ukraine December 5, 2022. REUTERS/Vladyslav Smilianets TPX IMAGES OF THE DAY 

A commander with the Ukrainian Army's 10th Mountain Assault Brigade sits, as Russia's attack on Ukraine continues, for a portrait outside his bunker shelter near the frontlines in the Bakhmut region of Ukraine, December 7, 2022. REUTERS/Shannon Stapleton 

A member of the 68th Independent Jager Brigade of the Ukrainian Army scans the horizon for Russian military from his position in the trenches near the frontline in the Southern Donbas region in Ukraine, November 29, 2022. REUTERS/Leah Millis 

Service members with the Ukrainian Army's 10th Mountain Assault Brigade eat lunch, as Russia's attack on Ukraine continues, next to their bunker shelter near the frontlines in the Bakhmut region of Ukraine, December 7, 2022. REUTERS/Shannon Stapleton TPX IMAGES OF THE DAY 

A service member with the Ukrainian Army's 10th Mountain Assault Brigade stands, as Russia's attack on Ukraine continues, next to their bunker shelter near the frontlines in the Bakhmut region of Ukraine, December 7, 2022. REUTERS/Shannon Stapleton 

Service members with the Ukrainian Army's 10th Mountain Assault Brigade unit prepare a BM-21 Grad self-propelled multiple rocket launcher, as Russia's attack on Ukraine continues, for launching near the frontlines in the Bakhmut region of Ukraine, December 7, 2022. REUTERS/Shannon Stapleton 

Servicemen of the Carpathian Sich Battalion rest at their positions on a frontline, as Russia's attack on Ukraine continues, near the town of Lyman, Donetsk region, Ukraine December 8, 2022. REUTERS/Viacheslav Ratynskyi 

Servicemen of the Carpathian Sich Battalion rest at their positions on a frontline, as Russia's attack on Ukraine continues, near the town of Lyman, Donetsk region, Ukraine December 8, 2022. REUTERS/Viacheslav Ratynskyi