A Game Changer or Just Another Crisis? A Bayesian Assessment of the EU’s Political Development After the Russian Invasion of Ukraine

Does war centralize authority in the European Union, or does the EU respond to military threat as it has responded to other crises? Russia’s invasion of Ukraine and the subsequent degradation of the American security guarantee allow a test of the bellicist “war-driven development” thesis (Kelemen and McNamara, 2022b; McNamara, 2026) against a “crisis-driven development” account that integrates its critics’ arguments into a single causal mechanism (Genschel, 2022; Freudlsperger and Schimmelfennig, 2022; Eilstrup-Sangiovanni, 2022). Using explicit Bayesian reasoning for qualitative research (Fairfield and Charman, 2022), I assess seventeen pieces of evidence on fiscal, coercive, and administrative capacity from February 2022 to October 2026, including process evidence on how EU institutions and member states negotiated the main instruments. Starting from equal priors, the evidence very strongly favours crisis-driven development (32 dB, odds of roughly 1,600 to 1). The EU relied on loan-based re-insurance, national fiscal space, and regulatory extension; when the Commission proposed binding central powers, member states removed them. Three pieces of evidence favour the bellicist thesis, and the result depends chiefly on how closely a slow-acting bellicist mechanism would mimic crisis-driven development in its early years. So far, the war has been another crisis rather than a game changer.