In the east Ukrainian city of Bakhmut, 15 kilometres (nine miles) from the positions held by Russian forces, an artillery unit waits for the signal. “Ready!” The four soldiers duck and put their hands over their ears. “Fire!” The shell shoots out of the cannon towards the Russian forces in a burst of flames and smoke. “According to the coordinates we received, the target is infantry,” says Oleksandr, 37, between two radioed orders. Oleksandr commands this small group of artillerymen, part of the Ukrainian army’s 58th motorised infantry brigade. Around 30 seconds later, the 50 kilo (110-pound) “fragmentation” shell, pinched from the Russians after their retreat from a nearby town, will explode above the position held by Moscow’s troops, showering them with its payload. A Ukrainian drone supports the operation “in real time”, monitoring the effectiveness of the strike from the old Soviet D-20 cannon in order to better calibrate the next one. Bakhmut, in the Donbas, has been the scene of active fighting for the last four months. Since the start of the Russian invasion in February, it is said to be one of the longest and most lethal battlefields for both sides, though there is no estimate of the exact losses. The front here has almost not budged since the beginning of October, despite a few small gains made by one or other of the opposing forces, only to soon be lost again. On the Russian side, Moscow is pushing hard, supported by mercenaries from the paramilitary Wagner group, sent to their death on the frontlines and dubbed “disposable soldiers” by the Ukrainians. For their part, the Ukrainians are holding their lines as they focus on a counter-offensive in the south, while trying to limit losses in the war of attrition being waged by the Russians. “As the military proverb goes: the sweat of the artillery spares the blood of the infantry,” says Oleksandr, who after another lethal attack on the enemy hopes to have saved the lives of some of his comrades.