The Ukrainian commander points ahead. There is a bridge over the Donets river, then forest. Behind lies the Russian city of Belgorod.

“That green hill over there is Russia,” says commander Roman Gryshchenko.

In September he helped push Moscow’s forces back across the border at Kharkiv.

The retreat marked one of the highlights of the Ukrainian counter-offensive in the north-east.

Now Kiev’s troops are so close to Russia in the village of Starytsya that some phones are mistakenly receiving text messages saying they’ve arrived in the country.

Grishchenko insists the area is now “absolutely safe” – but his troops are on guard.

They still face drone strikes, occasional artillery strikes and the threat of raids from Russian commandos, he says.

The 5,000-strong 127th Brigade he leads was formed from a force of volunteers and its mission is to defend positions in this retaken frontier zone.

The last official Ukrainian outpost lies in a ditch on a muddy road leading directly to Russia. Behind, special forces and border guards operate unseen.

A lone guard keeps his finger on the trigger and listens for suspicious noises in the woods.

A protected room underground with an internet connection functions as a digital monitoring station.

Soldier Sheleh, 32, taps a computer mouse whose red light glows in the gloomy room.

He inspects video footage of the area – mostly bushes and dirt roads.

“Here we monitor our side of the border, looking for possible crossing points that could be used for infiltration,” he says.

They work day and night and through bombing, he adds.

That morning, a dozen Russian soldiers were moving into Ukrainian territory before a brigade drone dropped a shell and forced them to retreat, according to video the 127th brigade sent to AFP.

This area was one of the first to be breached by tank columns sent through Belgorod in February.

Now that Ukrainian troops have taken control, Gryshchenko takes a tour of the retaken territory and revisits old battle scenes.

A Russian camp abandoned in the panic of retreat, with pieces on a chessboard still frozen mid-game.

A stretch of river used by Ukrainian forces to surprise Russian special forces in May.

And a charred tank, the first Russian T-90 destroyed in Ukraine.

For the commander, it’s a trophy. But he regrets that it was so badly damaged that his troops couldn’t reuse it.

“If we had had the weapons we have now in March, I would already be in Red Square in Moscow,” he said.