To save lives, Ukrainian combat medics must stay alive.

So, deep inside a position that soldiers call “the black forest” in eastern Ukraine, the medical corps of the 63rd Mechanized Brigade tries to remain hidden. The zero line — where Russian and Ukrainian forces are squared off in trench lines within sight of each other — is only a mile or two away.

The iconic red cross painted on the side of the team’s armored vehicle offers little protection from enemy fire. In fact, soldiers say, it makes them a target. They carefully camouflage the vehicle until it is needed — which is often these days as Russian forces mount wave after wave of assaults.

The vehicle is at the combat medic station, a critical link in the chain of care for soldiers wounded on the front. It is often the first stop before they are dispatched to stabilization points farther from the fighting and then to advanced medical centers where more complicated procedures, like amputations, are performed.

The medics at combat outposts provide basic trauma care, including setting bones, applying tourniquets, giving pain medication and, in some locations, performing blood transfusions.

The medics’ lives revolve around the routine.

“There are only two options: Either you are on duty or you are having rest,” said Lt. Andriy, a 27-year-old dentist who was mobilized in the summer of 2022 and is now a lead medic for the brigade. Like other soldiers, he asked that his last name not be used in accordance with military protocol.

“You wake up in the morning, get ready and go,” he said. “Without too much thinking.”

As he was talking, an urgent message crackled over the radio.

“Two men down. Fly out.”

It was time to go. Vasyl, the driver on duty, glanced up at the sky, looking for Russian aircraft.

“Currently, there are so many drones and kamikazes,” he said. “They are hunting us.”

Fortunately for them, the clouds hung low and heavy, limiting range of vision.

Vasyl pulled the armored vehicle out from under the brush, the soldiers checked their kit, and they set off once more.

They did not know it as they drove, but this would not be a rescue mission. The two Ukrainian soldiers had died where they had fallen. Once the team arrived, all they could do was wrap the bodies in black plastic bags and carry them away.

“The best experience is when you save a heavily wounded soldier,” Lieutenant Andriy said. “And the worst is when you can’t help.”

“I can’t call it a routine,” Lieutenant Andriy said. “It’s our duty. But you can’t get used to people’s pain.”

The scale and intensity of the war in Ukraine — which has ebbed and flowed over two years but rarely relented — can be hard to fathom. Combat medics and their teams often see the worst of it.

“You can’t describe it in words,” Vasyl said.

A train conductor before the war, he volunteered three days after Russia’s full-scale invasion began in February 2022. Since he spent 45 days in Bakhmut before it fell to Russian forces, nothing really shocks him anymore.

“Arms and legs, pieces of bodies,” he said, trying to describe what he had seen. “I felt hatred toward Russians. I was raised in a patriotic way. I love Ukraine. I was ready to defend it. And so now I am.”

While the weapons used to kill have evolved from swords and muskets to exploding drones and thermobaric bombs, soldiers die just as they have for centuries.

They bleed out. Organs fail. Trauma makes it impossible to draw a breath. Time becomes the enemy.

The stabilization medics are operating in what the American military refers to as the “golden hour” — the period of time when a life is saved or lost. Just traveling the short distance from their bunker to the zero line and back can take 30 minutes to an hour, often under withering bombardment, Lieutenant Andriy said.

“Once, as we went for evacuation at night, we accidentally drove to the Russian positions,” Lieutenant Andriy said.

Russian is commonly spoken by Ukrainian soldiers, and they did not immediately realize they were in enemy territory.

“We asked them if they had any wounded,” he said. “They said they had their own transport. We asked them to decide quickly if they needed assistance, as we needed to leave. They started surrounding our vehicle. We understood something was wrong.”

The Ukrainians jumped into their vehicle and raced away.

“The Russians were shooting at us,” he said. “But we managed to leave and even found our wounded soldiers that we were supposed to evacuate.”

The Ukrainian military does not release detailed information about casualties or statistics on the recovery of the wounded, but about 70 percent of all Ukrainian combat deaths and injuries result from Russian artillery and rocket barrages, according to the Global Surgical and Medical Support Group, an American nongovernmental organization. The group has been providing surgical support to Ukraine since Russia’s full-scale invasion began nearly two years ago.

Sometimes the fighting is so fierce that the medics cannot reach the front line to evacuate the wounded. They will wait to hear if they are needed at another location, then speed across bumpy roads to load wounded soldiers into armored vehicles, treating head wounds and other injuries as they head back to a stabilization point.

Electronic jamming and eavesdropping make it difficult to communicate the nature of injuries from the battlefield. Russia has repeatedly targeted medical facilities, the Ukrainian medics and the United Nations say, so field hospitals need to be both concealed and located farther from the front. Evacuation by air is impossible given the density of air defense near the front.

The treatment of wounded soldiers is also complicated by structural problems that are a legacy of the Soviet system: mismanagement, a dearth of trained instructors, tensions between medics on the ground and the command in the General Staff, and the reliance on volunteers to buy most supplies.

In November, President Volodymyr Zelensky dismissed the commander of the Medical Forces, Tetyana Ostashchenko, replacing her with Anatoliy Kazmirchuk, the head of a military hospital in Kyiv.

“A fundamentally new level of medical support for our military is needed,” Mr. Zelensky said when he announced the change. “From high-quality tourniquets to full digitalization and transparency in supplies, from high-quality training to honest communication with combat medics in those units that are functioning properly and efficiently.”

Lieutenant Andriy said he was sometimes surprised by how much his team could accomplish given the circumstances.

“No matter how exhausted we are, we know what we are fighting for,” he said. “We are fighting for our homeland. Our families and children are behind us. They would like to live in peace, to prosper, to be happy.”

“We will stand as long as needed,” he said.