And that is what Russia’s offensive has relied on in Ukraine’s eastern and southern territories. Relentless barrages of Russian artillery pummel everything in their way, destroying military positions and residential areas too.

According to Ukrainian authorities, the Russians are sending an extra 30 battalion tactical groups – some 22,000 troops – to the south to respond to Kyiv’s much-vaunted counter-offensive.

The arrival of American Himars and M270 multiple rocket launchers has given the Ukrainians the ability to destroy targets they couldn’t reach before.

But they say more are needed to counter Russian fire and to hit priority targets such as air defence, ammunition depots and supply routes.

Maj Gen Marchenko believes they will take Kherson back “in the near future” – and in a matter of weeks.

But in order to succeed they need to breach what he calls Russia’s static defence strategy: “We have to have three times more power, quantity of weapons and artillery. Unfortunately, we don’t have such an advantage. Therefore, we have to act in a non-standard way, drawing them out of their positions to equalise our power and resources.”

One of their non-standard tactics clearly involves artillery working in tandem with aerial reconnaissance groups. That could help to split Russian forces into smaller groups and encircle them without taking heavy losses, which would be unavoidable in an open confrontation.

“We have crossed the River Inhulets,” explains Maverick, “and now we’re trying to expand that ground, bring more equipment and cut off the Russian forces here into two groups – Kakhovka and Kherson.”

A key part of their strategy is to sever Russian supply routes in the south.

Maj Gen Marchenko says that in just two weeks Ukrainian armed forces have destroyed “more than 20 ammunition depots [in Kherson region], lots of command and control centres and other targets, including strategically important bridges”.

Bridges over the River Dnieper have been hit repeatedly at Kherson and Nova Kakhovka, and recent explosions at an airbase and ammunition depot in Crimea appear to be part of the same plan, even if Ukraine has not officially acknowledged its hand in those attacks.

But identifying such targets and guiding artillery strikes is a dangerous job. Maverick and his colleagues are closely monitoring an attack on a Russian vehicle that they believe can jam Ukrainian communication signals.

After a dozen rounds, the closest they can get to the target is 15m (50ft) before Russian forces respond. The terrifying whistle of a Russian shell sends everyone rushing inside a hangar to take cover. Missiles rain down around us. Mounds of earth rise like a fountain as shells hit the ground.

By now the Russians will know a drone team is directing artillery fire and they have started bombarding the area at random.

The drones are still out there and Maverick and his teammate are desperately trying to get them back.

“They’ve turned REB on!” shouts Maverick, warning of an immediate threat from Russia’s electronic signal-jamming warfare system.

With satellite navigation down and the remote control signal lost, drones become uncontrollable.

The soldiers survive the onslaught unscathed, but they have lost one of their drones.