Increased NATO defense spending alone cannot ensure the alliance’s security.

For the first time in the alliance’s 76-year history, a NATO ally engaged a Russian threat in its airspace. Polish air defense shot down three Russian drones, with additional downed drones later discovered across NATO’s eastern front. The incident represents a stress test of the alliance’s resolve during President Donald Trump’s second term, underscoring both Moscow’s willingness to probe NATO defenses and the alliance’s urgent need to bolster its readiness. While attention in the coming weeks will rightly focus on hardening air defenses and filling capability gaps, the Poland incident exposes a deeper vulnerability: NATO’s growing shortage of military personnel.

NATO currently lacks the manpower to meet its regional defense plans—let alone deter a growing Russian threat or deliver on its ambitious transformation pledges from June’s NATO Summit. Nearly all allies are struggling to recruit and retain enough troops to effectively deter a still manpower-heavy Russian military, even after accounting for Moscow’s enormous battlefield losses. Demographic decline and a widening civil-military gap further compound this challenge.

Even if allies meet the new pledge to spend 5 percent of GDP on defense, closing manpower gaps may prove harder than writing bigger checks. On average, NATO allies spend approximately 36 percent of their total defense budgets on manpower, with some like Italy spending nearly 60 percent. As NATO allies prepare to invest unprecedented sums in their collective security, they must simultaneously develop creative solutions to overcome recruitment challenges, expand their talent pools, and ensure that their ambitious defense plans are matched by equally ambitious workforce strategies.

Europe’s demographic crisis poses a direct threat to military recruitment. In 2022, EU births fell below 4 million for the first time since 1960. Simultaneously, decades of post-Cold War peace have left military service largely absent from the career considerations of young Europeans. A closer look at three alliance members demonstrates the extent of the challenge:

Germany: Berlin’s defense ambitions are most constrained by cultural resistance to military service. Despite important strides in military planning and resourcing, too few Germans may be willing to enlist to operate a larger force. Germany announced ambitions to increase its enlisted military personnel by 30,000 within six years to create Europe’s “strongest armed force.” However, these figures are still too modest to defend the country effectively. Berlin is already feeling the effects of being overstretched: Germany is the second-largest contributor of arms to Ukraine, and Berlin appears reluctant to commit troops to a Ukrainian peacekeeping mission due to existing manpower constraints. 

Norway: In 2024, Oslo announced an ambitious 10-year defense plan to bolster its security posture, which includes $60 billion in increased defense spending and capability acquisition. To resource this shift, Norway is taking steps to increase its armed forces by 50 percent by 2036. However, despite a highly respected and competitive universal conscription program, Oslo often struggles to convert these conscripts into career-track service members. With a maximum of 19 months for conscription, high turnover can also take a toll on the experience and continuity of the service as a whole. These trends are further magnified by Norway’s relatively small 5.6 million-person population. A country that currently struggles to field a requisite number of personnel will certainly be stressed to support an enhanced NATO alliance defense posture.

Italy: Like Berlin and Oslo, Rome already faces significant military personnel challenges and will likely struggle with recruiting in the future. Last year, its Chief of Defense Staff announced that Italy’s armed forces of 165,000 were “absolutely undersized” and anything below 170,000 was “below the level of survival.” However, unlike Germany and Norway, Italy’s personnel challenge has an easy fix. The average pay for service members is not competitive with private sector or government civilian salaries. Low pay, coupled with Italy’s relative distance from Russian aggression, dampens public support—only 16 percent of Italians say they would fight for their country.

These challenges are not unique to Europe. The United States faces similar demographic pressures, though with different causes, and has already had to adapt its recruiting practices to sustain force levels. This experience offers lessons that could help NATO allies translate defense spending into actual military capability.

Over the next 15 years, the number of American high-school graduates is expected to fall by about 13 percent (by 2041). But previous initiatives by higher education institutions to overcome declining birthrates could serve as a model for the US and allied militaries alike. These could include expanded offerings to underrepresented groups, such as women, minorities, and international students.

The United States military’s recent recruiting successes offer a roadmap for NATO allies. Facing similar demographic pressures, the US services exceeded 2024 recruiting goals through focused leadership attention, novel initiatives like boot camp preparation courses, and pragmatic policy changes: relaxing tattoo restrictions, allowing THC retests, and modernizing body composition standards. European allies could adopt similar approaches while addressing their unique challenges, such as Germany’s cultural resistance to military service and Italy’s uncompetitive military pay scales.

This is the lesson NATO must now embrace. The alliance’s historic commitment to spend 5 percent of GDP on defense is necessary but insufficient. Without enough trained personnel to operate its increasingly sophisticated equipment, additional funding will not translate into credible deterrence. 

Closing the manpower gap will require allies to adopt bold, coordinated strategies to expand talent pools, modernize recruitment policies, and foster a culture of excellence that attracts more talent and retains those already serving. A NATO that matches its financial investment with the right quantity and quality of human capital will be far more formidable than one that achieves only half the equation.