South Korea’s defense establishment is undergoing a significant contraction, with active-duty troop numbers falling by approximately 20 percent over the past six years due to declining birthrate. As of 2025, the military force has shrunk to around 450,000 personnel, down sharply from figures exceeding 560,000 in 2019—reflecting a recruitment crisis tied directly to a dramatic decline in the population of military-age males.
This downturn stems from the country’s plummeting birthrate: in 2024, South Korea recorded a total fertility rate of just 0.75 children per woman—the world’s lowest—marking an alarming demographic shift for the nation. This collapse in fertility or birthrate is reflected in the dropping pool of potential conscripts. The number of men aged 20, the typical age for enlistment, has diminished by 30 percent since 2019, now standing at roughly 230,000.
The South Korean government has already cut the length of mandatory military service to 18 months—shorter than the 36-month terms common in the 1950s—citing enhanced military capability through advanced technology and strategic alliances, particularly with the United States. Even so, the shrinking pool of draftees has strained defense manpower, especially among non-commissioned officers, where the shortfall hovers around 21,000 troops. The defense ministry estimates the country is roughly 50,000 troops below what it considers necessary to maintain optimal readiness.
Despite these personnel challenges, South Korea continues to invest heavily in defense, with its budget for 2025 exceeding 61 trillion won (about $43.9 billion)—a sum greater than the estimated size of North Korea’s economy. However, analysts warn that funding alone cannot fully offset workforce gaps if demographic trends remain unchanged.
Experts point to structural demographic change as a looming national-security threat: South Korea’s population peaked at around 51.8 million in 2020 and is projected to drop dramatically to 36.2 million by 2072. This decline underscores deep concerns about the sustainability of conscription-based military strength and long-term defense readiness.
In response to shrinking manpower, South Korean defense officials and analysts are exploring diverse mitigation strategies. These include increasing female recruitment, extended use of reservists, and accelerating modernization through technology—especially automation, unmanned systems, and AI-powered platforms—to make up for diminished human resources.
However, some experts caution that while modernization is critical, human capabilities remain essential. Talented, well-trained personnel are still needed to operate high-tech systems effectively, maintain discipline, and support operational flexibility.
This situation reflects a broader policy challenge: how to sustain a capable defense force while managing the cascading consequences of demographic decline—ranging from labor shortages to aging infrastructure—and how to ensure long-term military readiness in a nation whose population is aging and shrinking at historic rates.
