This paper analyses projections of defence expenditure in the Bucharest Nine (B9) countries in the context of NATO’s new commitment from the 2025 Hague Summit. Based on historical data and national declarations, we model two scenarios for development through 2035: the baseline trend and national ambition. The results show significant polarization within B9 countries. While the countries of the northeastern flank (Poland, the Baltic states) are accelerating toward 5.5% of GDP, the countries of Central Europe and the Balkans are converging more toward the baseline level of 3.5%. The study identifies the fiscal limits of this transformation and structural differences in the implementation of the new alliance goals.).