This essay proposes a new reading of Cohen's polemical text, Germanism and Judaism. It argues that the development of Cohen's late philosophy reveals him not as a helpless philosopher overwhelmed by the maelstrom of a world war, but as an "engaged" thinker who carries forward what he takes to be philosophy's duty to struggle against war by going to "war" in the space of theory and culture. Cohen's text needs to be placed in the context of his other wartime writings which, on the one hand, assigned a new and more radical function to messianic Judaism within his ethics, and simultaneously transplanted his neo-Kantianism into the more "realistic" political philosophies of Plato and of Spinoza, respectively. This essay argues that the thought of the later Cohen does not break with his previous commitments to cosmopolitanism and social democracy, as much as it tries to confront the harsh realities of European nationalist and anti-Semitic politics by articulating the roles of philosophy and of Judaism in modernity no longer through a strictly idealistic and cosmopolitan optic.