World War I questioned the hegemonic status of visual perception among the senses. The nineteenth-century military theorist Carl von Clausewitz had described the coup d’oeil as the ideal epistemological mode for a general of genius, but the battlegrounds of the early twentieth century could no longer be surveyed unaided—the long range of new weapons and faster vehicles made them too vast to be encompassed by a “stroke of the eye.” The development of camouflage techniques employing visual illusions as a military strategy reinforced awareness of vision’s fallibility. In this unsettling situation, listening became an increasingly important mode of perception for locating and identifying enemy activities on both sides of the front line. Telephony and radio were used to communicate, and new aural apparatuses such as the Richtungshörer (sound locator), invented by Berlin Gestalt psychologists Erich Moritz von Hornbostel and Max Wertheimer, shaped the war as an acoustic space. My project traces the emergence of these aural surveillance technologies, asking how their use provoked the development of strategies of deception to mask military activities and create an acoustic space of sound illusion. The strategies and technologies of listening actively generated and formed the soundscape of the War—employing artistic practices that blurred the divisions between art, science, and warfare.