This essay analyzes the infamously strange dialogue of For Whom the Bell Tolls (1940), in which characters speak English through a modified version of Spanish syntax, false cognates, and peculiar diction. It argues that Hemingway's creation of an Anglo-Spanish literary dialect represents not a political statement on the Spanish Civil War but an attempt to synthesize and recover the moments of interpenetration between English and Spanish since the 1600s. Hemingway's mode of dialogue in the novel is thus a “structural Spanglish” rather than the common code-switching form; it is a mode of interlingual writing that suspends the typical transaction of translation permanently between languages. Hemingway accomplishes this by using Spanish as a laboratory for his overlooked experiments in modernist mistranslation, which I trace through his development of cubist techniques in the novel and his debts to Ezra Pound. As he flattens semantic depth and fuses the syntaxes of two tongues, Hemingway actually invents an aesthetic language that corresponds to neither English nor Spanish, all filtered through a narrator who corrupts the translational process. He thereby creates a critical late modernist novel that looks forward to the depthless anti-epistemology of postmodernist writing. The essay concludes by sketching his place in this genealogy of contemporary writing.