Dr Achille Castrogiovanni is an independent researcher in international relations and security studies. He holds a PhD from the University of Sunderland and works on deterrence, hybrid conflict, critical infrastructure protection, NATO–EU security cooperation, maritime security, Russian strategic behaviour and escalation governance. His research has examined undersea infrastructure vulnerability, maritime coercion, narrative contestation and the legal-policy boundaries of collective defence and covert action. His work bridges strategic studies, security governance and cyber-physical resilience, with particular attention to how public authorities and infrastructure operators respond to grey-zone threats below the threshold of armed conflict.