“Eat it up quickly, while it’s hot and they’re not shooting,” says the bullet-proof-vested Oleksiy Kachko, opening a box of pizza in front of a group of surprised soldiers.

“This is for us?” the soldiers ask in amazement, smiling.

“The enemies are less than 80 metres from here. I reckon they can smell our pizza and their mouths are watering,” Kachko says.

Kachko, 23, previously fought in the Azov volunteer battalion and his partner in the deliveries, Bogdan Chaban, is also a 23-year-old former volunteer fighter.

Now they manage a pizzeria called Pizza Veterano in Mariupol, the only major city still under Kiev rule in the eastern regions that are otherwise controlled by pro-Russia separatists.

Opened in May, the pizza joint employs mostly veterans and people who have fled the war. One of the first things they did was to start delivering pizza to soldiers on the frontline, which is about 20km from Mariupol.

Kachko got the idea from watching the American television series Generation Kill about US troops in Iraq dreaming of hot pizza.

“We thought how cool that would be and it really did turn out to be very cool,” said Kachko, a tall man with striking blue eyes.

Wounded in the war, Kachko lost a lung and decided to use his veteran’s pension to open a cafe.

He and Chaban opened a franchise of the successful Pizza Veterano network launched in Kiev by another former soldier several years ago.

“It’s not just about earning money, it is employing veterans who find it very hard to get jobs,” Kachko says, while the pizzeria helps them with “adaptation to peaceful life.”

According to President Petro Poroshenko, more than 300,000 Ukrainians – many of them volunteers – have participated in Kiev’s military operations in the east since the outbreak of the conflict four years ago which has claimed more than 10,000 lives.

Kiev and its Western allies accuse Russia of funnelling troops and arms across the border to fan the flames of the conflict.

Moscow has denied the allegations despite overwhelming evidence that it has been involved in the fighting and its explicit political support for the separatists.

Every week Kachko and Chaban return to the frontline with pizzas, paid for with donations made online and in the pizzeria.

For security reasons they have to agree the schedule and route of their visits with the military command.

“Once a week we bring 20 large pizzas to the soldiers. It’s different units each time, we alternate them,” says Chaban, a slender bearded man wearing a cap with the logo of the US Special Forces.

He says he “gets a huge kick out of” bringing the takeaway treat.

This time it’s the turn of the village of Vodyane, whose residents have almost all fled the war.

“We try to make sure the delivery is done safely,” says Chaban, pressing hard on the accelerator of his dusty SUV as the road passes through an area of open steppe less than 300 metres from the rebel positions.

The delivery guys duck into a low dark trench hidden among tall grass and weeds.

Their appearance in the Ukrainian positions closest to rebel territory is greeted with pleasure.

The battalion is so close to enemy lines that soldiers are not allowed to use electricity and mobile phones, smoke cigarettes or even speak loudly.

The marines shake hands with their guests and thank them for bringing a hot dish, a welcome change from their cold soup and tinned food.

But it’s not the food that really matters, says Vadym Sukharevskiy, the battalion commander.

“When a soldier is stuck under constant fire and short of sleep and he sees a guy coming over with pizza, he realises he’s not alone, that there are many people behind him, praying for him and worrying about him, cheering him on to win and stay healthy.”