In the summer of 1944, during the Battle of Normandy, Allied forces – particularly the Americans – had become bogged down fighting the Germans in the Normandy bocage. This landscape of thick banked rock walls covered with hedges proved difficult for tanks to breach. In an effort to restore battlefield mobility, various devices were invented to allow tanks to navigate the terrain. Initially the devices were manufactured in Normandy, largely from German steel-beam beach defensive devices on an ad hoc basis. Manufacture was then shifted to the United Kingdom, and vehicles were modified before being shipped to France.