In the history of the left, the conjuncture 1914–1917 is the “bifurcation point” per definition. Leaving an enduring mark on the labor movement, it also shaped subsequent historiographies. For the pro-Bolshevik left, 1914 epitomized the betrayal of a group of reformist leaders. Conversely, anti-communist social democrats regarded the Second International as an uncomfortable political heritage. Despite irreconcilable disputes, both traditions shared a lack of interest in defending the period 1889–1914, let alone delving into its history. The real take-off of Second International historiography came later and coincided with the outset of the Cold War, experiencing a “golden age” in the 1960s and 1970s. Studies of socialism lost momentum from the 1980s onwards, but the last 15 years have seen a resurgence of interest in the Second International and even a popular reappraisal of Karl Kautsky. Linking historiography to wider social and political phenomena, this article reflects on this new interest in the Second International in both activist and academic circles. The first section summarizes the historical significance of the International and examines how the crisis of 1914 became a crucial “bifurcation point” with significant political and historiographical impact. The second section explores recent trends in scholarly research on the subject. The third section provides an analysis of the vindication of Karl Kautsky among radicals and socialists in the United States over the past 10 years. The conclusion summarizes the main arguments and reflects on the contribution this analysis can make to a discussion about the “long cycle” of socialism.