Spain's Maghreb Trilemma

When a secondary power shifts its strategic alignment, neighboring rivals do not respond uniformly: the coercive instruments they deploy reflect the material structure of their bilateral relationships rather than shared strategic preference. In this thesis, I develop a theoretical framework explaining how and why neighboring states select different coercive tools to influence a secondary power's alignment choices. The framework grounds tool selection in four structural factors: the pattern of asymmetric interdependence between coercer and target, the reversibility of the instrument, domestic audience costs for the coercing state, and the alliance cover available to the target. From these factors I derive three testable expectations: that coercers deploy the instrument for which they hold structural leverage (Tool Determination); that active rivalry between coercers amplifies coercive intensity (Rivalry Spillover); and that the target responds with insurance signaling toward external patrons (Insurance Signaling). This framework is tested through a case study of Spain's March 2022 decision to endorse Morocco's Western Sahara autonomy plan, analyzing its effects across three channels: Moroccan migration and border pressure, Algerian energy coercion, and Spanish NATO/EU alliance signaling. I develop a quantitative analysis of monthly irregular- arrival data from 2018 to 2024, employing difference-in-differences, interrupted time series, share-based specifications, and placebo testing, that attempts to formalize the migration channel finding. I find that Algeria and Morocco employed distinct coercive strategies reflective of their respective interdependence structures with Spain, consistent with all three theoretical expectations, and that Spain's response followed a realist insurance logic oriented toward its transatlantic and European alliances.