As East Asia Ages, Who Will Defend It? - Japan, South Korea, China | CNA Correspondent

East Asia’s Demographic Shift and its Impact on National Defense

Key Concepts:

• Demographic Time Bomb: Rapidly aging populations and declining birth rates leading to potential economic and security challenges.
• Super-Aging Society: A nation where individuals aged 65 and older constitute 20% or more of the total population.
• Security Dilemma: A situation where one nation’s efforts to increase its security (e.g., through military modernization) are perceived as threatening by other nations, leading to a cycle of escalation.
• Man-in-the-Loop: The level of human control and oversight in automated systems, particularly in military applications.
• Professionalization of Armed Forces: Transitioning from conscription-based military service to a fully volunteer, highly trained force.
• PLA (People’s Liberation Army): The armed forces of China.
• SDF (Self-Defense Forces): The armed forces of Japan.

Demographic Trends in East Asia

East Asia is experiencing a rapid demographic shift characterized by aging populations and declining birth rates. Japan was the first major power to become a “super-aging society” in 2005, with those aged 65 and over comprising 20% or more of the population. The Japanese population has been in decline for 16 consecutive years since peaking in 2009. Elon Musk has publicly warned that Japan may cease to exist due to its falling birth rate. South Korea currently has the world’s lowest birth rate, at 0.74 in 2024, prompting a “national emergency” declaration from former President Yun Seongyol. China, while entering this trend later, is aging at an alarming speed – taking only 36 years to transition from an aging to an aged society, compared to 115 years for France and 85 years for Sweden. China’s population declined for the first time since 1961 and has now been surpassed by India as the world’s most populous country.

Impact on Military Capabilities & Defense Spending

The shrinking youth populations are directly impacting the military capabilities of these nations. South Korea’s military has shrunk by 20% over the past six years, now standing at approximately 450,000 troops. Japan’s Self-Defense Forces (SDF) have a recruitment shortfall, with over 6,200 members quitting in fiscal year 2023 – the highest number in 15 years. The SDF, numbering around 247,000, faces limitations due to Japan’s pacifist constitution and the prohibition of mandatory military service.

Despite these demographic challenges, defense budgets are increasing across the region. Japan aims to raise defense spending to 2% of its GDP, exceeding its previous 1% target. South Korea’s 2026 defense spending is projected to reach 65.9 trillion won (approximately $45 billion USD). China’s defense budget has increased from 720 billion yuan in 2013 to 1.78 trillion yuan (about $250 billion USD) in 2025. Taiwan is aiming for 5% of GDP by 2030, up from its current 3%.

Strategies for Addressing Demographic Challenges in Defense

Several strategies are being explored to mitigate the impact of shrinking populations on national defense:

1. Immigration: Japan has been slow to embrace immigration, though attitudes are gradually changing. South Korea is more open to immigration, but it hasn’t significantly slowed population decline.
2. Technological Investment: All three countries (Japan, South Korea, and China) are investing heavily in technology, particularly robotics and artificial intelligence (AI), to compensate for manpower shortages. Japan, under the Takaja administration, is focusing on semiconductors and AI, but resource limitations pose a challenge.
3. Military Professionalization: South Korea is considering professionalizing its armed forces, moving away from a conscription system (currently 18 months of service, down from 30 months in the 1990s) and outsourcing non-combat functions to the private sector.
4. Increased Benefits & Wages: Japan is raising wages and improving benefits (clothing, food, housing, medical) for SDF personnel to attract and retain recruits.
5. Force Structure Restructuring: South Korea is investing in naval and air capabilities to compensate for the shrinking standing army.
6. PLA Modernization: China is deliberately reducing troop numbers as part of a plan to modernize the People’s Liberation Army (PLA), focusing on quality over quantity and technologically advanced equipment.

The Rise of Automation and AI in Military Doctrine

A significant shift is occurring in military modernization, moving away from a focus on the sheer quantity of equipment (tanks, warships, aircraft) towards automation and AI. China is currently leading the way in integrating AI into its military doctrines and operational concepts. This has prompted Japan and South Korea to follow suit, incorporating similar AI-based solutions into their military equipment.

However, the increased reliance on automation raises ethical concerns regarding human oversight in lethal decision-making ("man-in-the-loop") and the vulnerability of unmanned systems to attack.

The Security Dilemma and Potential for Increased Risk-Taking

The pursuit of technological advancements in defense is contributing to a “security dilemma,” where one nation’s efforts to enhance its security are perceived as threatening by others, leading to a cycle of escalation.

Analysts suggest that automation and AI may paradoxically increase a nation’s willingness to take risks, as the potential for human casualties is reduced. “If the risk profile changes because of automation and artificial intelligence, it may mean that even with a diminished population, states may decide that they are more they have a greater appetite for risky behavior, right? Because it's not people being, you know, uh put at risk or dying or getting harmed. It's machines that you will then replace.”

Unique Considerations for Each Nation

• South Korea: Faces a particularly acute demographic crisis and a significant military imbalance with North Korea (potentially a 1:4 ratio by 2040). Cultural and political sensitivities surrounding the inclusion of women in the armed forces pose challenges.
• Japan: Constrained by its pacifist constitution and a reluctance to embrace conscription. Labor shortages across all sectors make military recruitment competitive.
• China: Demographic challenges stem from the one-child policy, raising questions about public tolerance for casualties in potential conflicts, particularly over Taiwan. The PLA’s modernization is a deliberate strategy, but the reliance on only children in the military raises unique considerations.

Conclusion

East Asia’s demographic shifts present significant challenges to national defense. While increasing defense spending and investing in automation and AI are key strategies, they also introduce new complexities and risks. The region is entering a new era of security dynamics where military might will be determined not by troop numbers, but by the ability to process and act upon data effectively. The interplay between demographic trends, technological advancements, and geopolitical tensions will shape the security future of East Asia in the coming decades.