In a dugout near the front in Donetsk, the Guardian joins Ukrainian police officers turned pilots during a shift

The armoured car’s bumpy high-speed journey comes to a halt, and the Guardian team are dropped off in the November darkness, where two Ukrainians soldiers await. Using hard to detect red and green torchlight, they follow an unmarked trail across rough fields, punctuated by the sounds of frontline shelling, until a concealed opening appears. Inside, a specialist drone crew is at work.

Nearby, a drone flight of a few minutes away, is the frontline Donetsk town of Toretsk, where the Russian invaders have been gaining territory using surges of infantry and ceaseless artillery. Underground in the surprisingly warm bunker is a team of four Ukrainians, all members of the Khyzhak Brigade of police officers turned soldiers.