After many decades of indecision and foot dragging, U.S. allies are finally rearming. At NATO’s annual summit in June, the bloc’s members committed to spending at least 5 percent of their GDP on defense and related infrastructure. East Asian countries are belatedly building warships and missiles to counter a stronger, more assertive China. But even as funding rises, factories retool, and arms production ramps up, one question remains unanswered: Who will wield all these new weapons?
NATO states have not solved the fundamental problem of who will fight. One of the key lessons of the Russia-Ukraine war is about numbers. The era of limited counterinsurgency operations and quick precision warfare is over. As more than half a million soldiers face one another across a 1,000-mile front, we have had to relearn an old principle of war: Mass matters. And ultimately, that mass still rests on manpower.
Another key aspect of the Russia-Ukraine war—the mass deployment of drones on the battlefield—should not distract us from the centrality of manpower. Drones now account for an estimated 70 percent of casualties in the war, but they represent an evolution, not a revolution, in military affairs. Strike drones are often a more expensive and less effective means of fire support than old-fashioned artillery. The sizes of the drone fleets on Ukrainian battlefields therefore say as much about the exhaustion of traditional munitions, including artillery and missiles, as it does about the growing capabilities of unmanned vehicles and munitions.
Absent true autonomy—promised but not yet on offer—drones do not replace soldiers. On the contrary: “[W]hen it comes to people, technology is labor-intensive,” wrote the Royal United Services Institute’s Jack Watling, a keen observer of the Ukraine war. The expansion of drone warfare has caused the Ukrainian and Russian militaries to move people to new specialties, but it has not lessened the demand for soldiers.
Thus far, technology has not fundamentally changed the attritional nature of major state-on-state conflict. Inadequate Ukrainian mobilization efforts and shortfalls in Russian recruitment have begun to tell. But even as Russian and Ukrainian casualties eclipse 1 million, most European NATO states still rely on the small, professional forces typical of the post-Cold War era. At barely 70,000 full-time soldiers, the British Army is the smallest it has been since the 1700s. At around 180,000 full-time soldiers, the German Bundeswehr is about one-third of its Cold War size. For any Western European country, it would probably be a stretch to mobilize and deploy even one combat-ready heavy brigade in less than a week. For comparison: There are around 300 brigades on both sides of the front in Ukraine today, according to my conversations with military analysts and Ukrainian sources.
The situation is even worse in East Asia. Japan is the most important U.S. ally in the region. The Japan Self-Defense Forces (JSDF) are competent and field modern equipment, much of it of indigenous design. As China has become more assertive and bellicose, Japan has belatedly responded and is now midway through a significant increase of its defense budget over five years, with a long shopping list for new weapons.
But Japan’s Achilles’s heel is manpower. The military has not met its recruiting targets, falling short by nearly 10 percent last year. For junior service members, the numbers are truly horrible: The JSDF achieved just 30 percent of its 2023 recruiting goal for privates and equivalent ranks.
Many of those who do serve are of questionable readiness. Recruiting from a rapidly aging and shrinking Japanese population, the average age in the JSDF is nearing 40. Older service members are prone to more injuries and far lower combat availability, as Ukraine’s experience has shown. Aging also affects the force in less tangible ways: A dearth of junior leaders hinders leadership development and damages the morale and motivation of more senior officers.
With a large army and mandatory conscription of able-bodied adult men for at least 18 months, South Korea would appear to be an outlier among wealthy states. It can summon more than 3 million reservists and has a robust defense industry to arm them. But South Korea is firmly in the grip of a demographic crisis. Its cratering fertility rate—at 0.75 births per woman, a third of replacement level—has helped shrink the military by a staggering 20 percent in just the last six years.
Poland provides a good example of the diversity of manpower challenges facing armies today. A NATO member since 1999, Poland shares a border with Russia’s highly militarized Kaliningrad exclave. This puts Russian Iskander missiles just a few minutes of flight time from Warsaw. When Russia invaded Ukraine in 2022, Poland wasted little time in recognizing the threat to European security and reacting accordingly. Three weeks after the start of the invasion, Poland adopted the comprehensive Homeland Defence Act, which set a defense spending floor of 3 percent of GDP and spurred massive conventional rearmament, much of it with South Korean tanks and artillery. Polish military spending is now nearing 5 percent of GDP, the highest level in NATO.
In addition to deterring war and training to fight in case that deterrence fails, the Polish Armed Forces have a border security challenge. Neighboring Belarus, a Russian satrapy, has intermittently mobilized international migrants to try to storm the Polish border. In response, Poland has deployed up to 10,000 troops while strengthening fences and fortifications. The demands for soldiers don’t stop there: Last fall, another 20,000 or so soldiers were deployed for relief efforts after severe flooding in southern Poland.
Poland has rejected conscription as an answer to its manpower needs. Instead, it has instituted an unusual “voluntary draft.” Serving for up to 11 months, volunteer soldiers are given the best new equipment (while the regulars grumble) and recruited to join the professional force after their service ends. The regulars and volunteers are supplemented by a growing Territorial Defence Force of part-time soldiers, now more than 40,000 strong.
Reinstating an actual military draft has been politically toxic in the majority of Western nations for decades. All but a handful of NATO militaries terminated mandatory military service after the Cold War ended. But the tide is now coming back in. In Germany, Defense Minister Boris Pistorius has openly mooted restoring mandatory service, while the governing coalition has proposed a law to enable the swift reintroduction of conscription during a crisis. Even in Britain, historically averse to conscription as anything more than an emergency expedient during wartime, politicians such as former Prime Minister Rishi Sunak have discussed reviving national service.
Finland and Sweden, which only joined NATO after Russia’s full-scale invasion of Ukraine, might serve as models for other allies as they struggle to meet security challenges.
Finland, which has universal male conscription, can summon an army of nearly 1 million active soldiers and reserves from a total population of less than 6 million. Though it would take weeks to get all Finnish reserves mobilized, smaller high-readiness forces could be ready in days or even hours—a reaction to Russia’s surprise invasion of Crimea in 2014, which swiftly created a fait accompli. The Finnish Army also boasts one of NATO’s largest artillery forces and will soon be supported by 64 new F-35 fighters.
After a short hiatus, Sweden returned to its historic reliance on conscription in 2018 with a new system of selective, gender-neutral mandatory service. By drafting only 10 percent of graduating high school seniors, Sweden has created something unusual and perhaps even unprecedented: an elite conscript military. Though Sweden has twice Finland’s population, its reserves are still a fraction of its neighbor’s. But Sweden has doubled its conscript intake in just a few years while reinstilling a society-wide ethos of “total defence.”
The Finnish and Swedish conscription models offer a way out of Europe’s defense dilemma. But there is also a chance that highly publicized rearmament and heightened awareness of the security threat may bring in more recruits without coercion. The Bundeswehr, for example, has just announced an excellent first half of its recruiting year: more than 13,700 new service members, a 28 percent increase over the same period in 2024. The stagnating German economy may be a factor, but Russia’s invasion of Ukraine, the political and societal consensus behind rearmament, and the rising status of military service since the start of the Russia-Ukraine war also play a role.
Moderate coercion may also help. Under a proposed law pending Bundestag approval, all German men turning 18 will have to complete a digital survey on their interest in military service starting next year. Mandatory medical examinations will be reintroduced one year later.
Should the shooting start on NATO soil or in East Asia, volunteerism will prove inadequate to the manpower demands of major war. Ukraine has learned this old lesson, fitfully and perhaps fatefully. For all the singular fixation on spending targets, the best single metric for gauging a wealthy modern country’s dedication to its own defense may instead be the number of well-trained people in uniform. It is an open question whether the democracies of Europe and Asia will demonstrate this commitment.