As Ukraine's military steps up its strikes on Kherson, hinting at a new offensive to recapture the region, there is another force working alongside. They are Ukraine's shadow army, a network of agents and informers who operate behind enemy lines.
Our journey to meet the resistance fighters takes us through a landscape of sunflower yellow and sky blue to Mykolaiv. The first major town on Ukrainian-controlled territory west of Kherson, it has become the partisans' headquarters on the southern front.
Driving through military checkpoints, we pass giant billboards showing a faceless, hooded figure alongside a warning: "Kherson: The partisans see everything." The image is designed to make the region's Russian occupiers nervous and boost the morale of those trapped under their rule.
"The resistance is not one group, it's total resistance," the man standing in front of me insists, his voice slightly muffled by a black mask he's pulled up from his neck so I can't see his face as we film him, in a room I can't describe so that neither can be found.
I'll call him Sasha.
Shortly before this war, Ukraine bolstered its Special Forces in part to build and manage a resistance movement. It even published a PDF booklet on how to be a good partisan, with instructions on such subversive acts as slashing the tyres of the occupier, adding sugar to petrol tanks or refusing to follow orders at work. "Be grumpy," is one suggestion.
But Sasha's team of informers have a more active role: tracking Russian troop movements inside Kherson.
"Say yesterday we saw a new target, then we send that to the military and in a day or two it's gone," he says, as we scroll through some of the many videos he's sent from the neighbouring region each day. One is from a man who drove past a military base and filmed Russian vehicles, another is from CCTV footage as Russian trucks pass by, daubed with their giant Z war-marks.
Sasha describes his "agents" as Ukrainians "who have not lost hope in victory and want our country to be freed".
"Of course they're afraid," he says. "But serving their country is more important."
Working alongside Sasha are a team who fly drones into Kherson to spot targets for the military. Civilians, not soldiers, all are volunteers and they fundraise on social media to pay for their expensive kit.
The man in charge cultivated decorative plants before the war, but Serhii tells me he joined the fight to free the south after seeing the bodies of civilians executed in Bucha during the Russian occupation there. "I couldn't just stay at home after that," he says. "I didn't know what else I could do or think of, while this war is going on."
The task he chose instead is extremely dangerous. His team of four get shelled by the Russians every single time they go out, though no-one has been killed. "I know to some extent it's a matter of chance," Serhii shrugs, and breaks into a soft smile. "But at least if it happens to me, then I will know it was for a cause."
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Photographs by Sarah Rainsford. Eastern Europe correspondent, southern Ukraine.
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Ukrainian resistance fighters use drones to spot targets for the military