This chapter deals roughly with the period from the 1920s to the 1970s. From the ruins of WWI to the disintegration of the Keynesian paradigm, zero-sum thinking has appeared in guises ranging from models of self-sufficiency to their very opposites. First, we see the zero-sum implications of two principal aspects of autarky (essentially neomercantilism): one had to do with the symbiosis of state and big business at the expense of workers and other national economies (corporatism); the other is what found its foremost example in the ideology of blood and soil, namely the quest for national self-sufficiency at the expense of ideologically determined foreigners both inside and outside national borders. Amid the havoc wrought by autarky, the Bretton Woods agreement concretized the US Dollar as the world’s reserve currency and capitalism’s so-called golden age (of the national majorities at the expense of the minorities) in the decades after WWII. These Trente Glorieuses, fostered by Keynesian social democracy, had their own zero-sum features hidden underneath trickle-down narratives of eternal economic growth. The Cold War cracks began to appear during the 1970s, as the two nuclear superpowers were unable to keep their promises to their working classes, engendering yet more cycles of stagflation and zero-sum thinking and the collapse of Keynesian social democracies.