Economic Warfare and the Sea, 1650-1945

The recently published Economic Warfare and the Sea examines the relationship between trade, maritime warfare, and strategic thought between the early modern period and the late-twentieth century.  To celebrate the publication of this latest publication from our Research in Maritime History series, editors David Morgan-Owen and Louis Halewood have put together a short introduction to the book for those interested in finding out more.


Writing in 1897, the American naval officer and public intellectual Alfred Thayer Mahan wrote that ‘control of the sea, by maritime commerce and naval supremacy, means predominant influence in the world; because, however great the wealth product of the land, nothing facilitates the necessary exchanges as does the sea’. [1] For Mahan, history revealed the overwhelming importance of naval power to preserve and extend seaborn trade – or to deny it to an enemy. Wielding sea power in this manner had enabled Britain to become prosperous, building an economic world-system with the City of London at the centre, and rising to a position of pre-eminence among the great powers. This offered a blueprint for emerging, ambitious powers in the late nineteenth century, particularly the United States of America and Germany. Yet Mahan wrote at a time when other strategic thinkers, notably the British geographer Halford John Mackinder and Brooks Adams, seemed to question the continued utility of sea power. Would technological developments on land, notably the railway, not reduce the impact of sea power and blockade in future conflicts? This edited collection explores the crux of this debate, examining the utility of navies and the significance of economic warfare at sea across three centuries from a variety of transnational perspectives.

The volume contains chapters on a variety of different nations, regions, and themes, spread across four centuries of historical time. As editors, we have drawn out four key themes which our contributors have alighted upon – although there is certainly much more contained in the individual chapters themselves.

Our first theme is the historical significance of maritime economic warfare to the conduct of strategy at the national or imperial level. Approaching national or ‘grand’ strategy from this perspective allows us to foreground the pivotal importance of the sea to international affairs in a way which too many existing accounts underplay. In this respect, John Hattendorf reinterprets the significance of Britain’s devastating blockade of the United States during the War of 1812 to the outcome of the Treaty of Ghent. Matthew Seligmann re-evaluates the importance assigned to economic warfare within wider German naval planning prior to 1914, while Greg Kennedy provides a new perspective on Japan’s mastery of economic coercion in the Far East, as compared to the lacklustre combined deterrent presented by Britain and the United States, on the eve of the Pacific War.

The second core theme is the role played by state bureaucracies in campaign of economic warfare. Economic warfare was waged not merely at sea by navies, but by the broader apparatus of the state. Roger Knight emphasises the crucial tasks carried out by merchant captains in the British convoy system during the Napoleonic Wars, while John Ferris explores the enormous intelligence bureaucracy – with a focus on the role of postal censorship, conducted largely by women – which underpinned the British blockade in the First World War. As such, economic warfare must be seen as part of a broader picture of state power, and as an important additional dimension to the mobilisation undertaken to move national economies onto a wartime footing.

The third major theme of this volume concerns the significance of neutral powers to the conduct of economic warfare at sea. Economic warfare is global in its impacts and consequences, but also in its implementation, affecting all states involved in a globalised trading system, regardless of their belligerent status. Shining a light on the role neutral states have played in attempting to moderate the damage dealt to trading systems by economic warfare, as well as taking advantage of opportunities for targeted measures of economic coercion below the threshold of formal hostilities, affords a broader understanding of how economic warfare has functioned. Anna Brinkman explores these dynamics in her analysis of the role neutrality played within British grand strategy during the American War of Independence, while Maartje Abbenhuis examines how neutrality remained a credible strategic choice for great powers for much of the nineteenth century.

Lastly, this volume seeks to re-examine some of the foundational claims of ‘classical’ maritime strategists such as Mahan and his contemporaries regarding the benevolent relationship between sea power, economics, and strategy. Bleddyn Bowen’s chapter in particular reconsiders how renowned theorists of sea power, such as the British intellectual Julian Stafford Corbett and the French naval officer Raoul Castex, actually understood the role of economic warfare in the grand strategy of their respective states. In turn, it is important to recognise that the approach of strategic thinkers like Mahan have focused exclusively on economic warfare as pursued by states, neglecting the ways in which non-state actors have sought to utilise and benefit from economic coercion. As its final theme, then, this collection starts to redress this oversight by exploring how non-state actors interacted with, and sought to benefit from, episodes of economic warfare. Erik Odegard weighs the interaction between private organisations and formalised state navies in the Dutch Republic. Meanwhile, Silvia Marzagalli looks at how American shipowners responded to the disruption caused by the French Revolutionary and Napoleonic Wars, seeking to take advantage of the changing circumstances of trans-Atlantic trade. These myriad themes are bookended by two overarching chapters. Stephen Conway provides a tour de force on the development of the British fiscal-naval state and its use of economic warfare throughout the centuries of British naval mastery. The volume concludes with a reflection by Daniel Moran on how economic warfare at sea has evolved since the advent of the atomic age, and the relevance of it today.

Understanding the connections between sea power, economics, and international competition continues to matter today. 90 per cent of global trade is carried by sea, while 99 per cent of global digital communications are carried through sub-ocean cables. Great power rivalry has returned to the forefront of the global strategic agenda, notably in the South China Seas, posing questions over freedom of navigation in vital shipping lanes in East Asia. Meanwhile, incidents in the Persian Gulf involving merchant shipping and the Navy of the Islamic Revolutionary Guard Corps in early 2020 have had a direct impact on global oil prices, underlining the continued importance of seaborne trade to the supply of critical commodities. Exploring how state and non-state actors have conceptualised and used economic warfare at sea in the past provides a useful mirror for these contemporary debates about the utility of navies and the importance of merchant shipping, while better enabling us to understand the origins and intent of modern practices of economic coercion – better known as ‘sanctions’.

[1] Alfred Thayer Mahan, The Interest of America in Sea Power, Present and Future (Port Washington, 1897), p. 124.

Find out more about Economic Warfare and the Sea.

Follow us for more updates