Inside the 'kill-zone' on Ukraine's front line, where new weapons have transformed war

That is why Ukraine keeps soldiers like Kenya in small foxholes and dugouts inside the kill-zone, where they can do little more than stay and mark that territory.

Their biggest fear is being detected by the Russians. That's what happened to Khani, who spent 122 days at the front. He came to Ukraine as a Palestinian student in the 1990s and stayed.

Khani's position was in the basement of a two-storey house, when it was turned into rubble by Russian drones and artillery.

When the Russians tried to enter the basement, he and his fellow soldiers opened fire, revealing their positions.

"Once they knew we were there, they first dropped explosives from drones, then kamikaze drones attacked us," he recalls.

A drone attached to fibre-optic cables managed to fly inside the basement, but it became tangled up in its wires at the entrance and started spinning, so Khani shot at the cable reel and the drone lost connection with the pilot operating it.

At this point two Russian soldiers stormed his position. "They detonated anti-tank mines outside and destroyed the entrance, burying it under debris. They thought we were dead."

They survived thanks to a hidden exit they had dug just in case.

Granata, who recently left the front after 110 days, says the soldier he was with was badly wounded when Russian forces dropped an explosive containing gas in an attempt to force them to abandon their positions.

All supply routes in the Donbas kill-zone are now cut off, so food and ammunition has to be delivered to forward posts by aerial drones. But even they are unreliable: they often get destroyed or jammed, so supply deliveries have been intermittent.

Kenya said his meagre food supplies would often end up being eaten by mice. "They gnaw everything except metal. Because of the mice, we had to eat all food products except canned food quickly, or else the mice would destroy them all."

When asked what they lacked most in their foxholes, the soldiers all said it was water.

"The most memorable moment for me was when it rained," said Kenya. "I got undressed and went outside to wash myself."

During the winter, temperatures dropped to -25C, so old, worn-out sleepings bags were of little use when they slept on the frozen ground or a cold concrete floor.

Khani's partner fell ill and "one day he just didn't wake up," he said. He died of hypothermia.

Ukraine's military says Russian forces are regrouping along the front line, ahead of a possible summer offensive.

To counter that, the Ukrainians say they have increased attacks on Russian military logistics and supply routes.

This too may have slowed down the Russian advance. According to the US-based Institute for the Study of War, last month Moscow lost more territory in Ukraine than it managed to gain.

But it is still the foot-soldiers at the front of the kill-zone who still have the biggest task to hold on to Ukrainian territory. Without them, says Khani, the front line would collapse.