Government forces in Ukraine are trying to seize the initiative from Russian troops before the arrival of winter. A counter-offensive is already under way in the south and the Ukrainians are now preparing to expand that in the east to take back land lost in Donbas and around Kharkiv in the north. Quentin Sommerville and camera-journalist Darren Conway have been given exclusive access to a unit of Ukrainian troops.

The air is thick with the smell of burning sunflowers, and the pat-pat-pat of Russian cluster bombs can be heard landing across the fields, setting fire to a crop which stands, heads bowed, awaiting a harvest that's unlikely to come.

A self-propelled gun roars through the field, its caterpillar tracks tearing up the rich Donbas earth. The National Guard hold this ground in Ukraine's east - territory that Vladimir Putin has claimed as central to his war aims. It will be taken "step-by-step", he said. But for now, Russian progress has been reduced to a crawl.

And hanging heavy in the air, among the smoke and dust, is something else - expectation. Here in Donbas, and further north on the outskirts of Kharkiv, Ukraine's second city, the country's forces are braced for a counter-offensive.

I recently left army positions in the south, around Kherson. It is the only city that Russian forces have captured west of the strategically important Dnipro River. Those same troops are now engaged in battle, supporting forces who have broken through Russian lines in at least three places, as part of a long-planned counter-offensive in the south. Strict Ukrainian reporting restrictions are in place as the operation is under way.Here in Donbas, they remain tight-lipped. I'm not told the destination beforehand, and a unit press officer asks me not to name the regiment. He removes identifying patches from the men we film

Amid the din of artillery fire in a base under the cover of trees, Artyom, 35, says we are north of the city of Siversk, some 8km (five miles) from the Russian front line. "How close do you get to them?" I ask. "Thirty metres," he replies, "would you like to see?"

These are all defensive positions but the success around Kherson leads many to think that more offensives are planned here and further north.

I'm handed over to a red-haired guardsman who goes by the name of Svarog. He is 26 and baby-faced with a beard. "I'd look 18 without it," he says with a grin. But after six months of fighting, he's battle-hardened.

His unit saw its hardest fighting in July in nearby Lyschansk and Sivierodonetsk, where they were heavily outnumbered.

The fighting here is different. "They are not coming in such big numbers," Svarog says. "They no longer advance in battalion groups - they advance in a platoon, a detachment." One unit commander had explained that in the field they have one man for every three of the enemy. In Sivierodontesk it was one to seven.