No / Although military sites have long been the subject of geophysical investigation, those associated with recent military campaigns are noticeably rare. In fact, although such techniques are increasingly used to identify the unwanted legacy of modern warfare, such as unexploded ordnances or mass burials, they have not been used to investigate the archaeology of such conflict. The survey here attempts to identify the archaeology of one military site (Puits d'Herode) that was part of Hitler's Atlantic Wall and to identify the key elements associated with its D-Day defences. Magnetic gradiometry, twin-probe resistance and ground-penetrating radar were used at this site and, as a result of the nature of the buried archaeology, the magnetic technique proved most valuable. Trenches and bunkers previously known from aerial photographs were located accurately and a track believed to relate to the post-D-Day advance of the Allied forces across Puits d'Herode was also identified. The use of geophysical data in the investigation of this site has provided a new avenue to examine previously difficult topics such as the quality of intelligence available at the time of the conflict and the level and accuracy of shelling; although these may seem unlikely targets for archaeological geophysics, they are important to military historians for whom eye witness accounts are becoming increasingly scarce.