How did blockades shape the course, outcome and aftermath of the world wars? In both wars, belligerents sought to blockade their enemies, cutting them off from vital resources such as food, oil, information and capital to hasten their defeat. They thus impacted societies the world over, testing their resilience and vulnerability. They produced new forms of violence and humanitarian care, prompted innovation and learning, and had integrative and disintegrative effects on wartime societies, alliances and the world order. The special issue on “The Blockade in the Era of the World Wars” challenges orthodoxies that have been in place for decades, and stake out the ground for new research. It brings together experts from different historical disciplines and geographical specialisations to produce a nuanced, research-driven transnational and international history of the era of the blockade. Their contributions widen the focus from more traditional protagonists such as admirals, diplomats and government ministers to companies, NGOs, intellectuals and private citizens. They also consider just how strongly the blockade experience of the Great War affected preparation for and policy during the Second World War, not only in terms of raw materials or food, but also of know-how, law and mentalities. Finally, they integrate legal, military, economic, business, diplomatic, social and cultural perspectives, paving the way for an understanding of the world war-era blockades as a system that is larger than the sum of its parts.