• South Korea's military has shrunk by 20% to 450,000 troops over six years.
• The population of 20-year-old males, eligible for conscription, has decreased by 30%.
• South Korea faces operational readiness challenges and a significant shortfall in military personnel.

South Korea's military has seen a significant reduction, shrinking by 20% to about 450,000 troops in the past six years, largely attributed to a dramatic decrease in the male population eligible for mandatory service. This situation emerges from the country having the lowest birth rate in the world, currently at 0.75 births per woman, according to reports from Channel News Asia, South China Morning Post, and The Jakarta Post.

The decline in military personnel has resulted in a shortfall of 50,000 troops necessary for maintaining defense readiness. This shortfall particularly affects non-commissioned officers, which could lead to operational difficulties as identified by South Korea's defense ministry reports. Additionally, North Korea reportedly maintains around 1.2 million active-duty military members, intensifying concerns over security dynamics, as discussed in reports by BBC and Newsweek.

The anticipated decline in military recruitment stems from a projected 30% drop in the population of 20-year-old males, who typically form the core of new recruits. In response to these demographic shifts, South Korea's defense budget for 2025 is set to exceed 61 trillion won (approximately US$43.9 billion), reflecting a strategy to bolster military capabilities despite fewer personnel. The continued emphasis on strengthening defense aligns with various geopolitical tensions around the Korean Peninsula, according to several sources including Channel News Asia and South China Morning Post.

Experts have noted the need for at least 500,000 soldiers to effectively defend against North Korean aggression, which remains a constant reliance for the South owing to the ongoing armistice that marks the Korean War. The restructuring and modernization of military forces come amid lagging birth rates in a country now considered a "super-aged society", where the share of those aged 65 and older surpasses 20%. This demographic shift raises further challenges, as detailed by BBC and Newsweek.