Abstract. This paper analyses the compatibility between the expansion of military spending generated by the SAFE (Strategy, Armament, Financing, Efficiency) programme and the long-term fiscal sustainability of the European Union Member States, with a focus on the cases of Romania, Poland and Hungary. Starting from a dual theoretical framework: the crowding-out effect versus the Keynesian multiplier, the research applies the public debt sustainability equation (Δd = r − g · d + pb) and the fiscal multiplier analysis to assess the allocative efficiency of the programme. The results of the longitudinal comparison (2021–2026) demonstrate that the economic impact of the SAFE programme is non-linear and critically dependent on industrial absorption capacity: Poland transforms defence into a competitive advantage (multiplier > 1), while Romania experiences a structural deterioration in the trade balance (−1.2% of GDP). The conclusions emphasize that the economic sustainability of SAFE requires the localization of production, the implementation of the Fiscal Golden Rule, and the stimulation of public-private partnerships.

Keywords: military expenditure, fiscal sustainability, SAFE programme, defence multiplier, crowding-out, Eastern Flank.