In recent years border externalization has emerged as a central policy framework for European Union (EU) border and migration management. New multi-lateral and bi-lateral agreements on border management have been forged between the EU, its member states, and its North African neighbours and neighbours-of-neighbours. In the process, what is meant by the ‘border’ is being transformed with implications for where the border is located, who has jurisdiction over particular spaces, and how border and migration management is undertaken. This paper analyses the spatial logics of EU border externalization practices as they are being applied to and in North and West Africa. It focuses on Operation Seahorse and the transnationally coordinated border control projects and infrastructures implemented by the Guardia Civil of Spain. Seahorse serves as an implementation case of the Migration Routes Initiative, an approach toward migration management emphasizing interregional cooperation between designated origin-transit-destination countries. The initiative is the organizing strategy of the Global Approach to Migration, the EU’s overarching framework toward migration policy. The paper shows how Seahorse is changing migration policy and re-articulating Europe’s relations with African countries, producing new bordering processes, creating new geographies of integration and border management, and redefining the practices of territory, sovereignty, and extra-territoriality.