This soldier survived the siege of Mariupol and capture by Russia. What about all the others?

When the Russian tank turned its turret toward Hlib Stryzhko's position and fired, he thought his life was ending in a violent flash of light.

"I was aware that … I could die, lose my health or become an invalid — but I was ready to do it for Ukraine," he told CBC News.

The corporal in Ukraine's marines had been part of a group of hundreds of soldiers holding off a massively larger Russian force that was attacking the Illich iron and steel works plant in the northern part of the besieged city of Mariupol on April 10.

Somehow, Stryzhko not only survived the tank blast, which left him with horrific injuries, but he also lived through more than two weeks as a prisoner of war in Russia.

Now convalescing in hospital in the Ukrainian capital, Kyiv, he told his story of survival to our CBC News team.

Russia says it has more than 6,400 Ukrainian soldiers in custody — a number that was released before Russian troops seized control of the Donbas city of Severodonetsk last week. Ukraine's government has not said how many of its soldiers have been taken prisoner.

The ferocious battle may have led to the encirclement of even more Ukrainian divisions.

Ukraine has called for their prisoners to be released as part of a prisoner swap, but Reuters News Agency reports Russia's investigative committee is planning to put many of those men — including those who defended Mariupol — on trial for "crimes against peace." 

Human rights groups fear the proceedings will end up being show trials.   

Russia is also holding a number of non-Ukrainian soldiers as prisoners. Some are soldiers with dual Ukrainian nationalities while others came to Ukraine to join a legion of foreign fighters.

Britons Aiden Aslin and Shaun Pinner and Moroccan Saaudun Brahim have been sentenced to death by a court in the self-proclaimed Donetsk People's Republic, a decision that has been condemned by the United Nations.

Two former American soldiers who came to Ukraine to fight against the Russians are also now PoWs and there are fears they, too, could be handed death sentences.

For Stryzhko, 25, the decisive moment came as he was on the third floor of the Mariupol building spotting Russian troops when the tank broke through Ukrainian lines and its huge gun fired on his position.

"When a tank shoots, there is no time between the shot and the landing of that weapon, as with artillery," he said from his hospital bed.