Building on the success of various Commando Raids during 1941, Headquarters Combined Operations moved up the scale of size and complexity by electing to attack and deny the only dry dock that could take a German battleship for repairs, the Normandie Dock at St Nazaire on France’s Atlantic coast. However the port was miles up a well defended estuary. To deliver an explosive charge big enough to demolish the massive lock gates, an old ship HMS Campbeltown was converted to look like a German destroyer, so as to bluff their way into the heart of the port where it would ram the lock gates.The Commandos were to fan out across the dock to demolish pumps and winding gear to comprehensively deny the dock to the Kriegsmarine for a significant period of time. Under cover of dark the bluff worked well, up to a point, Campbeltown rammed the gates but the Commandos found that the Germans were alert and had great difficulty in reaching their objectives.