Soon after he deployed to Ukraine last fall, Pvt. Ivan A. Ovlashenko filmed a short video of himself wearing camouflage fatigues and an olive green fleece hat, sitting in a woods flecked with yellowing leaves while fellow soldiers nearby readied an artillery round to fire toward the Ukrainian lines.

“I am recording everything right,” he said, grinning before shouting a warning, “Mortar!” The clip was meant to reassure relatives back in Russia that his sudden transition to frontline artilleryman was coming along just fine.

Until it wasn’t.

Last September, President Vladimir V. Putin ordered the mobilization of 300,000 men to bolster sagging Russian defenses in Ukraine. At the time, the hordes of men who fled Russia to avoid conscription attracted the most attention. Yet hundreds of thousands of Russians like Private Ovlashenko — factory laborers and electricians, medical orderlies and basketball players, tractor drivers and school workers — went off to war.

The promise of payouts of $3,000 or $4,000 a month proved a huge incentive, along with appeals to machismo and the defense of the motherland. “What am I, not a man?” Mr. Ovlashenko told two women, his sister and his former wife. “I need to protect my country, my daughter.”

In lengthy interviews, the women said they were surprised how Mr. Ovlashenko, largely apolitical to this point, suddenly began parroting the government’s far-fetched talking point about the West planning to use Ukraine as a staging ground to attack Russia. If he did not fight in Ukraine, he said, he would have to battle the enemy on the streets of Bataysk, his hometown, a railroad hub just outside the southwestern city of Rostov-on-Don.

The mobilization shifted the calculus of the war. It was no longer some distant “military operation,” as the Kremlin still calls it, fought by contract soldiers, mercenaries and Ukrainian separatists press-ganged into service. Suddenly, ordinary Russians were thrust into the trenches.

Now, more than five months later, the tempo of dead and wounded returning to Russia is picking up, with zinc coffins arriving in places like Bataysk. It is a pattern repeating itself across Russia, even if the dead remain largely hidden.

“The numbers are secret,” said Max Trudolyubov, a Russian political analyst and newspaper columnist based in Vilnius, Lithuania. “The mobilized are from small towns, faraway places. The strategy is to spread the losses as thinly as possible across the country.”

Western intelligence officials estimate that 200,000 soldiers on the Russian side have been killed or wounded in the war. Of those, more than 16,000 have been confirmed dead in public sources, according to a project conducted jointly by Mediazona, an independent Russian news outlet, the BBC News Russian Service and volunteer researchers. While the true number is undoubtedly far higher, even that figure already exceeds the official death toll during the Soviet Union’s nine-year war in Afghanistan.

The dead include more than 1,366 new recruits, according to the project. Private Ovlashenko, 30, was one of them.

He grew up in Bataysk, a descendant of a long line of railroad workers, and was just 16 months younger than his sister, Valentina, with whom he was very close.

Valentina Strelkova, her married name, remembers her brother as a skinny, agile, fearless child — a potential circus acrobat. He remained devoted to his sister throughout his life, she said, dropping whatever he was doing whenever she needed him.

After he completed his compulsory military service, he went to work for Pepsi in merchandising.

Valeria Ovlashenka worked for Pepsi, too, in sales. When she spurned his advances, he gave a party for the entire staff, greeting her with a bouquet. He soon proposed, and the next day she discovered that she was pregnant. They married in March 2017, and their daughter, Polina, was born later that summer.

They quarreled frequently, not least over how to raise their daughter. Ms. Ovlashenka sought to replicate her own strict upbringing, while her husband made Polina the center of his life. He ironed her diapers and put her to sleep. He bought her toys and candy, took her to see the sea, and taught her to pick mushrooms in the deep northern forests. “It was always a holiday for the child,” she said.

They divorced after two years but neither dated anybody else, and Ms. Ovlashenka always hoped that they would reunite.

The mobilization summons on Sept. 26 came as a shock to his ex-wife and his sister, especially since Mr. Ovlashenko signed it immediately. “He was never interested or involved in political news,” said his sister.

He told his ex-wife of his decision to enlist when he was bringing their daughter back after a weekend, saying that he was leaving the next day. “He said it with such a smirk, as if he was leaving for a sanitarium,” she said, “I tried to talk him out of it.” She called the whole situation meaningless, arguing that he should stay home to raise Polina.

“I didn’t see my husband as a patriot,” she said. “I think that he just wanted a change of scenery.”

Mr. Ovlashenko’s father and sister drove to the training camp, more than an hour away, every day. They were given a list of necessities to rustle up — basically, everything except his flak jacket and helmet. They bought him warmer clothes, kneepads, a sleeping bag, a backpack and two balaclavas, among other equipment, spending more than $1,200. He was embarrassed, but grateful, and eventually the local regional government reimbursed them.

Mr. Ovlashenko was unexpectedly dispatched to Donetsk after just a week at the camp, his family said. During his earlier military service, he had been a driver. This time, he was assigned to an artillery unit. The newly mobilized soldiers received no training at the training center, he told them: “Everything I learned, I learned at the front.”

He never shared exactly where he was, but with each call, the sound of big guns rumbled ever louder. For the most part, he said things were “fine,” although he let the mask slip once. “‘You cannot imagine what I am doing here,’” he told his sister, sounding terrified. Then he clammed up.

Outwardly, his face became more masculine, sterner, his former wife said, while his eyes often got a frantic look that she recognized from their marital spats.

He did not talk about the dead much. Once, when his ex-wife asked about the commotion she could hear in the background, he said that the soldiers were drinking to commemorate fallen comrades. Another time he allowed that he had seen a lot of “cold” corpses, but few recently killed.

In December, after he suffered a light shrapnel wound in the shoulder, his calls became more frequent and more emotional. “It was like he burst,” said Ms. Ovlashenka. He sent money constantly for Polina — for clothes, a tree for the holidays, the circus and a ski trip.

When his ex-wife broached the topic of their reuniting, however, he backed off, and they postponed the discussion until he returned.

New Year’s Eve was the last time his sister spoke to him. “He was very cheerful, upbeat, positive,” she said. On Jan. 6, he called his former wife to ask if Polina liked her presents.

The last sign of life came on Jan. 9. When he could not talk, he would text an emoji like a smiley face.

Starting Jan. 10, there was a troubling silence. His sister dialed all the numbers he had called from, but nobody knew anything. Private Ovlashenko hugged her in a dream so vivid that she felt he had come to say goodbye.

On Jan. 14, the family learned from the Bataysk military recruitment office that he had been killed when a tank shell exploded in his trench near Makiivka, Ukraine.

They were told that his corpse had been shipped to nearby Rostov, to the main military morgue, but the military told them not to visit. The explosion had ripped his body apart, and they were having trouble identifying him. The family hoped that they had the wrong guy, but a fingerprint soon confirmed that it was him.

There was no open coffin at the funeral on Jan. 20. An honor guard fired off a salute in the muddy cemetery, and his father emitted a strangled cry, “Vanyuk!” — his son’s nickname — as they buried him, according to 161.ru, a regional online newspaper.

Polina, 5, was not at the funeral, but she knew about the war. Her mother initially told her that her father was on a long business trip, but Polina figured out from the calls that he was at the front.

At school, they took up a small collection, and they always mentioned her father when they talked about war heroes. Polina misses him terribly, and often encourages her mother to find her a new daddy. “I tell her, ‘Daughter, we don’t have a store where we can get a new daddy,’” she said. “There will always be one daddy. He’s in heaven.”

In late February, the family held the traditional ceremony marking 40 days since his death. They skipped the normal ritual of leaving food on his grave, as the local priest said it would be better to donate it to needy families.

“He had chosen a peaceful life, a peaceful profession, a nonmilitary specialty,” his sister said. “But his life completely disintegrated in a different way.”