During 1943, it had been recognised that there would be a requirement for a force of powerful aircraft capable of towing heavy transport gliders, such as the General Aircraft Hamilcar and Airspeed Horsa, it was found that the Stirling would fit this role admirably. During late 1943, 143 Mk.III bombers were converted as the "Stirling Mk.IV", with no nose or dorsal turrets, which was used for towing gliders and dropping paratroops, in addition to 461 Mk.IVs that were manufactured. These aircraft were used for the deployment of Allied ground forces during the Battle of Normandy and Operation Market Garden. On 6 June 1944, several Stirlings were also used in Operation Glimmer for the precision-laying of patterns of "Window" to produce radar images of a decoy invasion fleet.