Operations Executive and the American Office of Strategic Services. They identified the raid as an especially challenging one because the main targets, the university dormitories in which Gestapo had their headquarters, had civilian hospitals nearby on both sides, so precision was needed to minimise civilian casualties. A training area in 1:1 scale was drawn with chalk, where the pilots picked for the attack made two test runs before the raid. It was eventually decided that the attack would take place in four waves, about one minute apart: the first waves would carry regular bombs to blast open the buildings containing the Gestapo offices, while the last waves would attack with incendiary bombs to maximise the damage to the Gestapo archives. The bombs were set to explode with a delay of eleven seconds since in such a low level attack, the bombs had the potential to damage the aircraft that dropped them. It was also decided that it would take place on a workday, between 11:30 a.m. and noon, since few Danish prisoners would be held in the offices at this time, as most of them would have been escorted back to their cells elsewhere on campus for lunch, while the majority of the Gestapo staff would be present and preparing for the lunch break at noon. Three squadrons were to supply 25 aircraft, 24 Mosquito Mk.VI fighter-bombers and a Mosquito Mk. IV reconnaissance aircraft from the Royal Air Force Film Production Unit, to film the raid. Twelve Mustang Mk. III fighters from 315 (Polish) Squadron would escort them, to defend the bombers from fighters based at the German airbase at Grove and create confusion by attacking minor German targets around central Jutland. All aircraft would carry extra fuel tanks to make sure they could make the long trip across the North Sea. The destination and target of the mission were not disclosed to the pilots until their final briefing at 8:00 a.m. on 31 October. On 30 October, the date and time for the raid was settled for the next day at 11:30 a.m. As a final preparation, the aircraft and crews involved in the raid gathered at the airbase at Swanton Morley at 8:00 a.m. on the day of the attack for a final briefing. When the fighters from 315 (Polish) Squadron landed, it was discovered that four of them had broken tailwheels, so it was decided to proceed