South Korean military experiences sharp decline of pool of able-aged men

South Korea’s military has contracted by 20% over the past six years, driven largely by a steep drop in the number of men eligible for mandatory service in the country, which has the world’s lowest birthrate, according to a new report.

The shrinking pool of enlistment-age men is also creating a shortage of officers and could lead to operational challenges, the defence ministry warned in the report, as reported by The Guardian.

The findings were submitted to Democratic Party lawmaker Choo Mi-ae, whose office released the document this week.

South Korea’s armed forces have been steadily downsizing since the early 2000s, when troop numbers stood at roughly 690,000. The decline accelerated in the late 2010s, leaving the current force at about 450,000 soldiers.

Military leaders have attributed shorter mandatory service periods—now averaging 21 months, according to the 90 Day Korean website—to enhanced capabilities. These improvements have been supported by a military alliance with the United States and a homegrown defence industry that has become a significant arms exporter, The Guardian reported.

By comparison, North Korea maintains an estimated 1.2 million active-duty troops, according to the defence ministry’s 2022 figures. In the North, conscription applies to both men and women, lasting up to 10 years or more, depending on gender.

Government data shows that between 2019 and 2025, the number of 20-year-old men in South Korea—a typical enlistment age following a physical exam—fell by 30% to just 230,000.

South Korea is also one of the fastest-ageing societies in the world, with a fertility rate of just 0.75 in 2024—the average number of children a woman is expected to have in her lifetime.

The national population, which peaked at 51.8 million in 2020, is projected to drop to 36.2 million by 2072, according to government forecasts.

By Nazrin Sadigova