Prior to the launch of Operation Cobra (an American offensive during the Normandy campaign), solutions were developed for how tanks could effectively support the offensive within this terrain. Bulldozers or tanks modified to carry a bulldozer blade were used to open gaps in hedgerows. Some hedgerows were so thick that engineers first had to blow a hole in the bank, which a bulldozer would later clear and widen. This time-consuming process slowed down the progress of the Allied offensive, and was compounded by the problem of the conspicuous bulldozers and dozer tanks being targeted by German gunners to deny the Allies a means to break through. Throughout July "innumerable" inventions were created by various American units to get tanks through the hedges quickly without exposing their weak underside armor. A hedgecutter developed by the 79th Infantry Division was in operation by 5 July, and a few days later, XIX Corps demonstrated a set of prongs that had been initially developed to create holes for the placement of explosives. The force of these prongs were able to lift and remove a portion of the hedgerow, enough so that the tank would be able to push on through to the other side. Units within V Corps also invented devices, which were dubbed 'brush cutters' and 'greendozers'.