With the American built M4 Sherman Tank available to Allied forces in large numbers, the British decided to match their successful 17-pounder anti-tank gun with the latest version of the Sherman, in the hope that they could produce a tank capable of challenging the feared German Tiger and Panther heavy tanks. Requiring quite significant redesign of the turret and with the gun mounted on its side, the 17-pounder equipped Shermans became arguably the most effective Allied tanks of the Second World War and were easily capable of knocking out any German tanks they encountered following the Normandy landings. Given the name ‘Firefly’, unwary German tank commanders who assumed this new Allied tank was just a standard Sherman were in for an unwelcome surprize and they quickly learned to be wary of the longer gun barrels of the Sherman Fireflys.