Weaponizing Interdependence in the Grey Zone: How Hybrid Threats Convert Economic Leverage into Security Erosion

Economic coercion and security erosion are routinely treated as correlated outcomes, yet the causal pathway connecting them is rarely specified. This article asks through what mechanisms hybrid threats with an economic component convert economic leverage into the erosion of targeted states' internal and external security. It identifies a gap at the meso level: weaponized- interdependence theory explains how asymmetric network positions become coercive instruments, and securitization theory explains how issues acquire existential urgency, but the two literatures seldom meet, and neither traces the bidimensional propagation of an economic shock. The article proposes a mid-range causal model, the economic transmission belt, comprising the weaponization of interdependence at a network choke point under conditions of strategic ambiguity, an external transmission pathway into alliance and military dynamics, an internal transmission pathway into fiscal and societal strain, and a securitizing move that elevates the disturbance to an existential register and feeds back into the strategic environment. The model is examined through process-tracing across three deliberately heterogeneous, non-great-power episodes that vary by initiating actor and coercive vector: Western financial-exclusion measures on Iran, the Eastern Mediterranean maritime-resource dispute involving Turkey, Greece, and Cyprus, and the 2021 closure of the Gazoduc Maghreb-Europe between Algeria and Morocco. Evidence tests of differing inferential weight are applied transparently. The findings indicate that the mechanism is actor-agnostic, that securitization intensity and substitutability condition outcomes, and that internal and external erosion can decouple. The contribution integrates two separate theoretical traditions into a single, testable process model of economic-to-security conversion.