After 225 days stuck in a front-line foxhole, the Ukrainian infantryman's muscles were so weak he could barely walk. His commanders had tried five times to swap him with another soldier - but they could never reach him. Rotating soldiers on the front line in eastern Ukraine is extremely difficult because of the constant threat of drones.

This area near Kostyantynivka is currently one of the most dangerous hotspots, and the Ukrainian military admits that Russian forces have reached its outskirts. Known as Kenya, the infantryman took two days to walk 11km (6.8 miles) to get back to his brigade, avoiding mines and hiding from drones.

Ukraine's 93rd brigade has the job of defending Kostyantynivka and its surrounding towns and villages from Russia's advance. If this highly strategic city falls, Moscow will be able to push towards the last remaining Ukrainian strongholds in the Donbas region – Kramatorsk and Sloviansk.

Kenya's task was to maintain his position and listen for any movement outside, engaging only if Russian troops tried to move against them. Most fighting was done by drones, he said. And these weapons have transformed how wars are fought.

This is a grey zone along the front line within the range of drones piloted remotely from both sides. Every time when we had to come out of our positions, we prayed we would come back alive, Kenya shared.

Drones cannot seize positions; they cannot control heights and crossings. Even in the age of robots and remotely operated weapons, the old rule of war still holds: without boots on the ground, an army cannot hold territory.

Kenya and others like him are living through what appears to be the paradox of modern warfare. As machines increasingly replace humans on the front lines, the role of troops becomes more critical in either seizing or defending land.

The harsh realities of frontline life also involve rationing supplies. Food deliveries often come through aerial drones which are frequently destroyed or jammed, forcing soldiers to make do with what little they have, often eaten by vermin.

As Ukraine braces for a potential Russian summer offensive, soldiers like Kenya remain essential to holding ground, maintaining the fragile balance on this frontline.