Deterring the Seabed: A Strategic-Theory Framework for Undersea-Infrastructure Defence in the Post-Accession Baltic

Although the Baltic Sea has seen more suspected attacks on critical undersea infrastructure than any of the world’s other waters since 2022, the policy literature offers only incident chronologies rather than any strategic theory of how such acts might be deterred. This article supplies one. It argues that seabed coercion defeats the classical dyad of punishment and denial for three compounding reasons: the acts are deniable; they fall below the armed-attack threshold; and the target cannot be defended at scale. Drawing on maritime strategy and cyber and cross-domain deterrence scholarship, it adds detection, entanglement, and an emergent deterrence by legal-jurisdictional cost to the repertoire. It also isolates the central obstacle: deterrence by detection deters detection, not action, unless bound to a credible, pre-declared response. It then develops a layered posture for the post-accession Baltic and explains why no single instrument suffices.