International socialism prior to World War I overcame internal disunity and external obstacles by developing a new style of political culture and communication centered on mass-based demonstration. This culture consisted of a diverse repertoire of activities such as public display, political symbolism, the popular press, the issuance of manifestos, massive antiwar rallies, and the convening of impressive political spectacles. As the largest international movement of its era, international socialism articulated a powerful indictment against the European imperialist and militaristic order. Claiming to represent all of humanity and to reconcile national and international identity, international socialism facilitated the expression of political dissent, the expansion of democratic citizenship and the spread of innovative techniques we now consider an essential part of modern political communication and culture. This interdisciplinary book touches upon several fields of scholarship including European Socialism, political communication, social movement, peace studies and World War I.