An army of engineers from Ukraine’s phone companies mobilized to assist policymakers and the public during repeated Russian drone and missile strikes.

Engineers, who are often unnoticed and unsung in peacetime work round the clock to restore or maintain phone service. Sometimes they even risk their lives to do so. They started generating power to keep the towers afloat after Russian strikes knocked out the electricity they used for their phones.

“I know my guys, my colleagues, are exhausted,” Yuriy Dugnist of Ukrainian telecommunications company Kyivstar said, after he had walked through a foot (15 cm) of fresh snow to reach a fenced in mobile phone tower at the western edge of Kyiv.

Dugrist and his colleagues shared a glimpse into their daily routines. They use an app on their phones to track which towers are receiving electricity. This is either during the periods of controlled blackouts to conserve energy, or when generators kick in to provide back-up power.

One entry reads in English “Low Fuel” and is very alarming.

Before their rounds began, they stopped at a service station to fill up eight 20-liter (5.3-gallon) jerrycans full of diesel fuel. This was used to fill up a large tank that houses a generator that powers a tower that is 50 meters (160 feet) tall in a suburb village without electricity for many days.

This is one of many towns in Ukraine that have been without power for a while, or even none at all, since the multiple Russian strikes on the country’s infrastructure in recent weeks — especially power plants.

Kyivstar, Ukraine’s largest mobile phone company, has 26 million customers. This is roughly two-thirds the population of Ukraine before Russia invaded. Many have returned since then, but many are still living abroad.

Although the diesel generators were placed at the base of the cell towers long before the invasion they were seldom used. To help Ukraine maintain electricity supply after Russia’s invasion, many Western countries offered similar transformers and generators.

After an emergency blackout caused by Russian strikes on Nov. 23, Kyivstar sent 15 teams of engineers to assist the mobile stations and “all our resources” called in to help them.

He recalls running to the location of the destroyed cell tower as Russian forces pulled out from Irpin (a suburb northwest of Kyiv) earlier this year. He reached there before the Ukrainian mineswepers arrived to give the all clear signal.

According to reports, the price of satellite phones alternatives such as Elon Musk’s Starlink, which Ukraine’s military used during the conflict’s 10th month, has increased due to the strain it is putting on its mobile phone networks.

Following widespread infrastructure strikes last week in Ukraine, President Volodymyr Zilenskyy met with top officials to discuss restoration and supplies to protect the country’s energy- and communication systems.

He said that “special attention is paid to communication system” and added that “we must keep communication,” no matter what Russia may have in mind.