Using Eric Hobsbawm’s notion of the “short 20th century”, it is argued that international politics during the 20th century was not so much a struggle between different state forms. Rather, it was a product of the various responses to the underlying social conflicts stemming from the emergence of the working class and socialist movements, themselves a consequence of capitalist development. And on the same lines, it is suggested that the post-war liberal order can be identified in terms of a form of social constitutionalism that reflected these twin social settlements within advanced industrial countries as well as within the structures of the global multilateral system. The death of post-war liberalism can only be understood in terms of the collapse of the broader project of social democratisation that marked the “short 20th century”.