How South Korea’s military has shrunk by 20% to just 450,000 active troops

South Korea’s military is facing a growing problem: it’s running out of soldiers.

A new defence ministry report shows that the size of the South Korean army has fallen by 20 per cent in just six years, to just around 450,000 active troops.

The sharp decline is tied to a steep drop in the number of men of enlistment age, a consequence of South Korea having the world’s lowest birth rate, the report said on Sunday.

But why does this matter so much? And what does the state of the military actually look like? Here’s a closer look.

Shrinking South Korean military

The most immediate reason for the decline is demographic. The pool of men aged 18 to 28, the group eligible for conscription, has been shrinking at a rapid pace.

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Government data shows that between 2019 and 2025, the number of 20-year-old men, the age when most who pass the physical exam begin their now 18-month-long mandatory service, fell by 30 per cent to just 2,30,000.

South Korea’s military has been getting smaller for decades. Back in the early 2000s, the country had around 690,000 soldiers. By 2019, that number had dropped to roughly 563,000, and the pace of decline has only picked up since then.

The number of military divisions has also been cut significantly, from 59 in 2006 to just 42 today, with many units either disbanded or merged to make up for the shortfall, BBC reports.

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Why this matters

South Korea’s shrinking pool of eligible recruits is not just a problem for filling enlisted ranks, it’s also creating a shortage of officers, a gap that could cause serious operational challenges if left unchecked, according to the defence ministry report made public by Democratic Party lawmaker Choo Mi-ae.

The concern is heightened as the country is still technically at war with its nuclear-armed neighbour, North Korea , which is believed to have an active-duty force of about 1.2 million troops, based on the defence ministry’s 2022 estimates.

That imbalance in troop numbers, the report warned, puts South Korea in a “structurally difficult position to succeed in defence.”

To maintain a credible deterrent, it urged “decisive action at the national level” to keep the military at no fewer than 500,000 troops. Currently, about 21,000 of the shortage is in the non-commissioned officer ranks.

To slow the decline, the defence ministry has floated several measures, from increasing the recruitment of female soldiers to offering bonuses for short-term service to cutting the number of men assigned to noncombat duties. But critics argue these steps won’t be enough to solve a problem rooted in demographics.

A senior defence ministry official, speaking anonymously, acknowledged that growing advanced technology can help, but only to a point. “There are limits to replacing people with technology, especially when facing a heavily armed adversary right across the border,” the official told The Korea Times.

Choo stressed that the issue requires urgent attention, warning that the debate is not abstract. “It’s a matter of who will be there to defend the country when the time comes,” she said.

South Korea’s birth rate plummets to a new low

The shrinking size of South Korea’s army is part of a much bigger problem, the country’s rapidly ageing and declining population .

South Korea has held the unwanted title of the world’s lowest birth rate for years, but new figures show the situation is worsening.

According to government data, the total fertility rate, the average number of children a woman is expected to have in her lifetime, is just 0.75 in 2024, which is far below the replacement rate of 2.1 needed to maintain a stable population.

This means each new generation will be significantly smaller than the last, with fewer young people to enter the workforce and serve in the military. 

The country’s overall population, which peaked at around 52 million in 2020, is now projected to shrink sharply in the coming decades, is expected to shrink to 36.2 million by 2072.  

Despite billions spent on subsidies, housing incentives, and childcare support, surveys show many young South Koreans are reluctant to have children due to high living costs, long working hours, and concerns about job security. Others cite a lack of work-life balance and changing social attitudes toward marriage and parenthood.

With input from agencies