The South Korean military has decreased by 20 percent in the past six years, now totaling approximately 450,000 troops, primarily due to a significant decline in the number of young men eligible for mandatory military service, according to a report released recently.
South Korea currently holds the lowest birth rate in the world, which is causing a dramatic reduction in the pool of men available for military duty. This demographic shift is also leading to a shortage of officers and could create operational challenges if the trend continues, the report from the South Korean Ministry of Defense warns.
The report was submitted to Choo Mi-ae, a member of the ruling Democratic Party, and later made public by her office.
The military has been steadily shrinking since the early 2000s, when it had around 690,000 active personnel. The decline accelerated in the late 2010s, with numbers dropping to about 563,000 active soldiers and officers by 2019.
In comparison, North Korea is estimated to maintain an active military force of around 1.2 million troops, according to the latest 2022 Ministry of Defense assessment.
Between 2019 and 2025, the population of 20-year-old males—a typical age for conscription—has decreased by 30 percent, down to about 230,000, according to government data. This is the age when most men who pass physical tests are drafted for mandatory military service, which currently lasts 18 months.
The military attributes the shortened service period to improvements in capabilities, enabled by its alliance with the United States and South Korea’s growing defense industry, which has become a major arms exporter. For reference, conscripts served 36 months in 1953, at the end of the Korean War armistice.
South Korea’s defense budget for 2025 is projected to exceed $43.9 billion, surpassing the estimated entire economy size of North Korea.
Despite the substantial budget, the military still faces a shortfall of 50,000 troops necessary to maintain defensive readiness. Approximately 21,000 of these missing personnel are non-commissioned officers, the Ministry of Defense stated.
South Korea is one of the world’s fastest aging societies and had the world’s lowest fertility rate at 0.75 in 2024, meaning an average woman is expected to have less than one child in her lifetime.
The country’s population, which peaked at 51.8 million in 2020, is projected to fall to 36.2 million by 2072, based on government forecasts.
