British geologists participated for more than a year in the planning of “Operation Overlord,” the Allied invasion of northwest France. Following D-Day on June 6, 1944, they contributed to the subsequent 11-month operational phase in western Europe, including the initial 3-month battle for Normandy.

Beachhead maps were prepared prior to the invasion at 1:5,000 scale from published topographic and geologic maps, aerial photographs, and secret ground reconnaissance. They indicated the character of the beaches and cliffs, distribution of different surface sediments, and other factors likely to affect cross-beach mobility. Airfield suitability maps were made to indicate the distribution within enemy territory of candidate areas for the rapid construction of airfields. After the invasion, between June 7 and August 13, 1944, 20 airstrips, mostly 1,100–1,500 m in length, were completed in the British occupied area of Normandy. Geological information was used to guide the systematic development of road metal. Initially, weak Jurassic limestones were quarried, as at Creully; later, stronger Paleozoic quartzites were worked, as at Mouen, southwest of Caen. Stone produced by the Royal Engineers in Normandy quickly rose to a peak monthly total of more than 140,000 tonnes in August 1944. Water supply intelligence and the control of well siting and drilling were geologist's responsibilities. In 1st Corps area, about 50 water points were established, with 12 operational at any one time. Water in Normandy was obtained largely from rivers and existing wells, supplemented by 33 new boreholes.

Geologists were also used to assess the effects of aerial bombing; soil conditions affecting cross-country vehicular movement; ground conditions for river crossings; and the nature of the sea floor beneath the English Channel. Normandy thus provides a case history of British military geology “par excellence.”