The familiar story of Britain's First World War is one of massed armies of citizen soldiers on the battlefields of Europe and the Middle East. This book offers a fresh perspective, placing the seas and oceans at the forefront of how Britain fought between 1914 and 1918.Britain was the world's maritime power. British coal, ships, businesses, and infrastructure were crucial to seaborne trade. The City of London was the global financial centre. These enviable advantages were a source of prestige and power. Their geopolitical potency was latent in peacetime, but after the outbreak of war Britain exploited its influence over the maritime world to orchestrate a novel form of warfare on a global basis. The sea allowed Britain to fight a war of machines and mobility, and to mobilise vast economic resources in the process. In 1914 it was unclear how to translate Britain's maritime and economic position into wartime advantage. It required new forms of interaction between the state and the economy. Maritime business possessed knowledge and expertise that became crucial to how the state made war. Complex new arrangements between business and the state were necessary to meet the demands of conflict. Through them, Britain combined commercial networks and state power to embark upon an ambitious project of economic statecraft. This endeavour sought to re-make global trade in pursuit of coalition war-making in the industrial age. The sea was crucial to this process, and seapower epitomized how Britain fought the First World War.