Domenico Losurdo reconstructs the genesis of Heidegger's philosophy in its historical context, analysing the meaning and characteristics of the peculiar 'ideology of war' developed in Germany at the outset of the First World War. In the 20th century, conflicts between states took the form for the first time of total war requiring the mobilisation of an entire society. This all-pervasive ideological mobilisation of consciences was associated at the purely military and industrial level in a form never seen before. On the one hand, among the allied nations the ideology of war centred on the principle of 'democratic intervention', the Wilsonian idea of a holy crusade able to subvert the eternally militarist and autocratic Germany and, in this way, favour a kind of great 'international democratic revolution.' On the other hand, in a spiral of radicalisation, the German ideology of war characterised the looming conflict as a great clash between irreconcilable civilisations, faiths, world-visions, and even races. Germans affirmed not only the superiority of their culture over the enemy countries, but above all the hypothesis of a political and social model that expelled from modernity every universalistic concept of emancipation and democratisation. Moving within this milieu, Heidegger's philosophy contested the cultural decadence and 'massification' reigning in Western industrial society. In a sharp confrontation with the entire philosophical tradition starting from ancient Greece, he finally condemned the conceptual basis that is the foundation of the modern world as a form of degenerated Platonism in which liberal, revolutionary, and Marxist ideas, and even Nietzsche's philosophy, were involved. Contrary to the majority of interpreters of Heidegger's philosophy, Losurdo reconstructs Heidegger's political dimension and shows the influence of historical and social forces on the development of his ideas.