Nets, Barriers, and Illusions - Passive Defences in Naval Warfare from World War I to the Present

This article examines the historical development, technical design, and strategic value of non-explosive naval traps, with particular emphasis on anti-submarine nets, harbor obstructions, decoy minefields, and fake moored mines used as psychological deterrents. Drawing on a wide range of archival naval manuals, operational histories, doctrinal publications, and scholarly analyses, the study traces the evolution of these passive defensive systems from the First World War through the Cold War and evaluates their effectiveness across different maritime environments. Through comparative analysis, the article demonstrates that non-explosive naval traps consistently shaped adversary behavior by restricting maneuver, increasing uncertainty, and imposing operational delays, often achieving strategic effects disproportionate to their material cost. Case studies including the Dover Barrage, major defended harbors of the Second World War, and Cold War port defenses illustrate both the strengths and limitations of such measures, particularly when integrated into layered defense systems combining surveillance, active patrols, and lethal weapons. The article further explores the contemporary relevance of these historical practices, arguing that advances in sensors, unmanned systems, and data-driven maritime awareness create renewed opportunities for passive and deceptive defenses in modern naval strategy. By situating non-explosive traps within broader debates on deterrence, area denial, and maritime security, this study contributes to a more nuanced understanding of how low-visibility, non-lethal measures can exert enduring influence in contested littoral and harbor environments.