Last month, Japan released its latest annual defense white paper. The document has a great deal to say about the threats now confronting the island nation, ranging from an increasingly assertive China to a nuclear North Korea. But one of its most important themes concerns something else entirely: the changing nature of warfare itself.
Japan, the white paper lays out, needs to prepare for a battlefield that is increasingly dominated by autonomous systems, by artificial intelligence, and by long-range standoff weapons. Tokyo’s Defense Ministry has made adapting to these “new ways of warfare” a major priority.
That shift is already becoming visible. Japan is now investing heavily in unmanned systems as part of a new, multi-layer approach to coastal defense. The plans are ambitious, and include everything from small attack drones to unmanned surface vessels and underwater craft. The process is being overseen by the Defense Ministry’s dedicated Acquisition, Technology and Logistics Agency, which has already selected a number of drone manufacturers for a rapid technology development program.
All this makes good strategic sense. The current conflicts in Ukraine and the Middle East have showcased the utility of advanced platforms, both as offensive long-range weapons and as tools for surveillance, targeting and defense. Like other militaries around the world, Japan’s is absorbing those lessons.
But Tokyo’s investments in autonomous technologies are significant for another reason as well: demographics.
By now, the island’s dismal population prospects are exceedingly well known. Beginning in the mid-1970s, Japan’s total fertility rate fell below “replacement” – the 2.1 live births per woman that nations need to maintain a stable population, without factoring in migration – and never recovered. The result is an extended demographic contraction that is continuing to accelerate.
Last year, Japan registered just over 670,000 births, the lowest number since record-keeping began at the end of the 19th century. Meanwhile, its fertility rate has fallen to 1.14, one of the lowest in the world.
The resulting trendline is stark. In its 2025 national census, Japan’s population tallied at roughly 123 million, more than three million less than five years earlier. By this summer, it had declined further still, to roughly 122.7 million.
And even steeper decline seems to be in store. Japan’s National Institute of Population and Social Security Research projects that, under its “medium scenario,” the country’s population will fall to approximately 91.6 million by 2065, and 87 million by 2070. By then, nearly four in ten Japanese will also be 65 or older.
All this has clear implications for the Japanese military. The country’s Self Defense Forces (SDF) are already significantly undermanned; as of this spring, the SDF had 217,701 personnel in uniform, significantly less than the authorized force strength of 247,154.
Recruitment, meanwhile, is lackluster, something Japanese defense officials have explicitly linked to the country’s declining birthrate and a shrinking pool of military-age citizens. Those pressures, moreover, are likely to intensify even further as Japan’s working-age population contracts, because the SDF will find itself competing with private industry for the same progressively smaller pool of candidates.
That poses a real problem, because Japan’s foreign policy horizons are getting broader. Recent years have seen successive governments reinterpret Japan’s self-defense constitution to permit more ready and robust responses to mounting regional challenges. This posture has been reiterated by Japan’s current Prime Minister, Sanae Takaichi, who has signaled that her government could have an active response in the event of a “survival-threatening situation” like a Chinese invasion of Taiwan.
All of which goes a long way toward explaining why Tokyo is now prioritizing advanced defense technologies. In the face of adverse (and persistent) demographic trends, automation offers at least part of the answer to how Japan is planning to keep pace with regional threats.