Disguised in a balaclava, Andriy recounts one seemingly endless firefight when they came under attack by a flood of Wagner fighters.

“We were fighting for about 10 [straight] hours []. And it wasn’t like just waves; it was uninterrupted. So it was [] like they didn’t stop coming.”

“They make the group – let’s say from 10 soldiers – reach 30 meters, then they start digging in to keep the position,” Andriy says of Wagner.

Another group follows, he says, to claim another 30 meters. “That’s how, step by step, (Wagner) is trying to move forward while they lose a lot of people in the meantime.”

When the first wave is exhausted or cut down, Wagner sends in more experienced combatants, often from the flanks, to overrun Ukrainian positions.

Andriy says facing the assault was a frightening and surreal experience.

“Our machine gunner was almost [going] crazy because he was shooting at them. And he said, I know I shot him, but he didn’t fall. And [later], when he maybe bleeds out, he falls.”

Andriy compares the battle to a scene out of a zombie movie. “They’re climbing above the corpse of their friends, stepping on them,” he says.

“It [seems] very likely that they are getting some drugs before the attack,” he says, a claim that CNN has not been able independently to verify.

Even after the first waves were eliminated, the attack continued as the Ukrainian defenders said they ran out of bullets and found themselves surrounded.

“The problem was that they went around us. And that’s how they surrounded us. They came from the other side. We didn’t expect them to come from there."

“We were shooting until the last bullet, so we threw all the grenades [a few guys and I had and left]. We were helpless in that situation.”

They were lucky. Held off until the last moment, the Ukrainian fighters say, Wagner withdrew at the end of the day.