In the course of its civil war of 1936-9, Spain hosted thousands of foreign soldiers from across the world. Amongst them were the approximately 35,000 volunteers of the International Brigades, the likes of whom identified General Francoߣs rebellious Nationalists with a global fascist offensive and rallied to the defence of the embattled Republic. The introduction to Making Antifascist War argues that their encounters with the people, places and politics of Spain were not an incidental sideshow to the more important business of fighting fascism, but a key component of their transnational military service. Cross-cultural contact was not only more diverse than often assumed, but also more consequential ߝ not least by feeding into the motivations, identities and actions of thousands of soldiers. After establishing the nature of that contact, the introduction argues that it enabled the foreign fighters to engage in a creative process of defining the Spanish Civil War in their own partisan terms. It does so by engaging with sources, methodologies and questions pertinent to the cultural history of war, with a particular emphasis on the role of transnationalism.