ZARICHNE, Ukraine — Kyrylo Horbenko was 16 years old in the summer of 2023 when he and two dozen of his male friends walked into an army recruitment office in east Ukraine and announced they wanted to fight Russian troops on the front lines.

The officials on duty laughed them out, telling them to come back when they were adults. The others later lost interest or went abroad, Horbenko said. But he enlisted immediately after turning 18 in March.

Kyrylo Horbenko signed up for combat in Ukraine through a generous new government program. SVET JACQUELINE FOR WSJ

“Who is going to fight, if not us?” the gangly teen asked as he prepared for his army induction course at a training ground in east Ukraine last month.

What separates Horbenko from the thousands of battle-hardened soldiers he will soon serve alongside is that when he signed up, he secured for himself an interest-free mortgage, a rare chance to vacation abroad and the first installment of a sign-on bonus totaling a 1 million Ukrainian hryvnia, equivalent to about $24,000—a sum that exceeds many experienced soldiers’ yearly pay.

The fresh recruit is among hundreds who have signed up since February through a generous new government program aimed at enticing Ukraine’s youngest adults into the country’s badly depleted armed forces. The numbers signing up so far are modest. But Ukraine’s leaders hope that in time the program, known as Contract 18-24, will help chase down a demographic they have largely sought to spare from the front lines.

That they are doing so reflects the severity of the manpower deficit that has hobbled Ukraine’s defense effort in the face of a relentless Russian onslaught in the country’s east. Most men willing to fight signed up long ago, and enlisting more is getting harder each year. Many eligible men—those between 18 and 60 who are banned from leaving the country—are either in hiding or have paid bribes to flee the country illegally and escape the draft.

Kyiv has sought various ways to replenish its ranks after almost 3½ years of full-scale war. It has raided nightclubs, allowed convicts early release from prison and unveiled billboards throughout the country proclaiming: “Everyone is going to fight.” Last year it lowered the age of compulsory military service from 27 to 25, which only temporarily boosted numbers.

Western allies have long called on Kyiv to lower the age further, but Ukrainian President Volodymyr Zelensky has rebuffed such calls, arguing Ukraine needs its youth to rebuild the country once fighting ends. “It’s very important for me to safeguard the lives of our people, our youth,” he told a French newspaper in December.

Meanwhile, 18- to 24-year-olds have been largely free to get on with their lives—even as commanders argue that their verve and energy would bolster Ukraine’s aging and exhausted force.

That is where Contract 18-24 comes in. It dangles various perks in return for a one-year commitment to the military, and alongside the 1 million Ukrainian hryvnia it offers a monthly salary equivalent to almost $3,000, six times the national average in Ukraine. There is also free college tuition and discounted dental care.

A recruitment push for the program has featured TikTok videos, viral social-media posts and shiny billboards that stand on the central streets of Ukraine’s major cities—all of them with a Gen Z twist.

One video posted in March to the TikTok account of Ukraine’s Defense Ministry asked: How many McDonald’s cheeseburgers does 1 million hryvnia buy in Ukraine? (The answer, apparently, is 15,625).

Ukraine’s move to attract new recruits with high salaries and mortgage help echoes similar moves in Russia, which has managed to bring tens of thousands of men into its armed forces by offering generous sign-on bonuses that dwarf average salaries in most parts of the country.

Russia last year announced an expansion of its armed forces by 180,000 people, to 1.5 million active service members. Zelensky said in January that Ukraine has almost a million people in arms, and officials say the army is adding 30,000 people a month.

But few young people are swayed by Contract 18-24 so far. The government says only around 500 have joined the scheme since it launched in February. A wall of bureaucracy often delays the process of onboarding recruits, and many get cold feet or drop out under pressure from their parents, according to Ukrainian officials, who caution that it is still too early to judge its success.

Behind the program’s slick promotional campaign is a tough decision it places before Ukraine’s youth.

With no peace on the horizon despite a monthslong diplomatic push by President Trump , male Ukrainian teens often say the choice before them is to either join the military or to try a professional career that may be cut short by mobilization once they turn 25. Many choose emigration instead.

Timur Ushak plans to move to Slovakia. Photo: Svet Jacqueline for WSJ

Timur Ushak has watched as one classmate after another has moved abroad from his town in east Ukraine, mostly to Poland or Germany. The 16-year-old is now studying the Slovak language ahead of a planned move to Bratislava for university studies next year.

“If I leave, I know it’s probably for good,” said the tall, athletic teenager, who says he has lost faith in Ukraine after 10 years of conflict that is drawing ever closer to his town, Kamianske. “I don’t believe the war will end.”

There is also some resentment among older Ukrainian servicemen, who dislike the preferential treatment of the Contract 18-24 cohort. The generous sign-on bonus of 1 million hryvnia has inspired a mocking nickname for its participants: “the millionaires.”

Maj. Yevheniy Hromadsky , a 24-year-old soldier who in 2022 received the Hero of Ukraine medal, the country’s highest military award, said he earned only 12,000 hryvnia a month when he fought in the defense of Kharkiv in the first months of the war—a battle in which he lost his father.

Hromadsky, who joined the military at the age of 18, said there is a subtle generational divide between his peers, who experienced their formative years after Russia annexed Crimea and invaded east Ukraine in 2014, and those who are teenagers today.

Most young Ukrainians became desensitized to the risk of war when the conflict with Russia abated between 2018 and 2021, Hromadsky said. Those years of relative peace, he argues, bred complacency and decreased their willingness to fight.

He argues that the best way to keep Ukraine’s army staffed is to introduce two years of mandatory military service between the ages of 18 and 20, after which conscripts can receive a university education at the state’s expense.

“The army needs logisticians, we need engineers,” Hromadsky said. “We need people with a higher education.”

Maj. Yevheniy Hromadsky said there is a subtle generational divide between his peers. Photo: Svet Jacqueline for WSJ

Horbenko, the fresh Contract 18-24 recruit, is aware that his enthusiasm for military service is unusual. He has spent years preparing, researching weapons and Ukrainian army units, and tracking Russian and Ukrainian battlefield advances.

After high school, while still underage, he took a job at the post office. While he helped dispatch humanitarian aid packages to troops on the front, he spent his days wondering: Why should I sit here, hiding away?

The day he signed his military contract in March, he drove past his mother’s workplace to share the news before continuing on to the training base where he is now staying. She told him: I knew this day would eventually come.

“It’s because others are hiding from recruitment officers that 18-year-olds like me are signing contracts,” Horbenko said.

Oleksandr Bahach, another recruit, waited months for the military to get in touch after he turned 18 and registered his interest last year. Several weeks ago, he saw an online ad for the 18-24 program and submitted an application that was quickly approved.

“I would collect all the men in the country and send them to the front,” said the 19-year-old. “The bitter truth is that we’re losing this war.” Bahach cites Bakhmut, Avdiivka and other key battles of the war as inspiration for his decision to fight.

The two young men are now preparing to take their oath of service and begin basic military training for Ukraine’s 25 undefined Airborne Brigade. After a month and a half, they will be allowed to choose a specialization in the brigade. After another 4½ months of specialized training, they will serve half a year on the front lines.

They spend their evenings at the training ground watching videos of Ukrainian military operations to ready themselves mentally to be in trenches for real, or familiarizing themselves with their new equipment, including radios and tactical bodywear. Horbenko worries he is too emotional and short-tempered and is steeling himself for what is to come.

“I’m preparing for the worst, so that when it happens I can stay calm and handle it,” he said.

Write to Matthew Luxmoore at [email protected]