South Korea’s active-duty armed forces have contracted by one-fifth in six years, dropping to about 450,000 troops, according to a Defence Ministry report presented to parliament. The decline accelerates a longer-term downsizing from roughly 690,000 soldiers in the early 2000s and leaves the services about 50,000 personnel short of the level the ministry considers necessary for full operational readiness, with non-commissioned officers accounting for nearly half of the gap. The shortfall stems largely from demographics. Government data show the number of 20-year-old men—those who typically enter the 18-month mandatory service—has fallen 30 % since 2019 to 230,000. South Korea’s total fertility rate slipped to 0.75 in 2024, the world’s lowest, and the overall population is projected to shrink from a 2020 peak of 51.8 million to 36.2 million by 2072. Officials say improved weaponry, a long-standing alliance with the United States and a growing domestic defence industry allow shorter service periods than the 36-month terms imposed after the 1953 armistice. Nonetheless, the manpower decline heightens concern given that North Korea is believed to maintain about 1.2 million troops. Seoul’s 2025 defence budget surpasses 61 trillion won (US$43.9 billion), larger than estimates of the North’s entire economy, yet the ministry warns that continued demographic pressure could complicate force maintenance if unaddressed.