Another concern is Poland’s national debt trajectory. While its debt-to-GDP ratio remains moderate at 50% as of 2023, rising defense expenditures could push borrowing higher. If Poland finances its military buildup through debt rather than revenue growth, rising interest payments could strain public finances in the long run. A comparison with South Korea, which has sustained high defense spending while maintaining fiscal discipline, suggests that Poland may need to increase defense industry exports or diversify its financing sources to sustain its military expansion without endangering economic stability.

It’s Demographics, Stupid

Beyond financial considerations, Poland faces a more fundamental challenge: a shrinking and aging population. The number of men aged 18–39 fell from 6.1 million in 2000 to 5.2 million in 2023, a decline that will accelerate in the coming decades. The country’s fertility rate is one of the lowest in the world, and Poland’s total population is projected to shrink from 38 million today to around 34 million by 2050. By then, the median age will rise from 42 to nearly 50, raising questions about the sustainability of an expanded armed forces.

The previous conservative PiS government aimed to increase Poland’s military to 300,000 professional soldiers, a goal the current liberal government of Donald Tusk has maintained in principle. However, recruitment difficulties suggest this target may be unrealistic. Poland’s military currently stands at 200,000 troops, and attracting 100,000 additional personnel in a tightening labor market will be increasingly difficult.

A key challenge is that the military must compete for workers with both the private sector—where wages and conditions are often more attractive—and other public services such as law enforcement and emergency services. The average salary in the Polish military stands around 9000 PLN ($2200 USD) per month, a bit more than in the private sector, but conditions tend to be poorer. The question remains whether this will be sustainable in light of  Poland’s strong wage growth and a hugely expanding number of military personnel.

A Global Problem

Poland is not the only country  facing demographic constraints on its military expansion. In South Korea, which has the world's lowest fertility rate (0.72 in 2023),  active-duty military has already shrunk from 620,000 in 2017 to 500,000 in 2022 due to a declining pool of young conscripts. Russia, experiencing its own long-term demographic crisis, has resorted to aggressive conscription policies, i.e. the recruitment of foreign fighters, and even the use of convicts to replenish its forces. Ukraine, where wartime losses and emigration have accelerated demographic decline, has been under pressure to lower the conscription age to sustain its military. In April 2024, President Zelensky reduced the draft age from 27 to 25, acknowledging the urgent need for more troops but also the risk of Ukraine’s irreversible post-war demographic collapse, should these cohorts suffer heavy casualties.

These cases highlight an emerging reality: the mass mobilization of young men may soon become unfeasible in many developed countries. As a result, Poland—like its peers—may have to rethink its approach to military human resources.

Poland is entering uncharted territory—both as NATO’s most ambitious military spender and as a country grappling with severe demographic decline. Whether it can sustain this trajectory will depend not just on financial resources but also on its ability to adapt to the realities of 21st-century warfare. If Poland succeeds, it may set a model for other NATO nations facing similar demographic constraints. If it fails, its military ambitions may ultimately be limited not by budgets or political will, but by a simple question: Who will serve?