South Korea’s military has shrunk by 20% in the past six years, largely due to a sharp decrease in the population of men of enlistment age for mandatory service in the country with the world’s lowest birthrate, according to a report.

The sharp decline in the pool of men available for military service is also causing a shortfall in the number of officers and could result in operational difficulties, the defence ministry said in the report.

The report was made to the ruling Democratic party member of parliament Choo Mi-ae, whose office released it.

The size of South Korea’s military has declined steadily since the early 2000s, when it had about 690,000 soldiers. The pace accelerated during the late 2010s and there are now about 450,000 troops.

North Korea is believed to have an active-duty military of about 1.2 mn, as per the latest estimate by the defence ministry in 2022. The population of 20-year-old men in South Korea declined between 2019 and 2025 by 30% to 230,000, as per government data. Twenty is the age when most men who pass a physical exam enlist for military service.