 The unit assigned to destroy the battery was the 9th Parachute Battalion , part of the 3rd Parachute Brigade , commanded by Lieutenant Colonel <unk> Otway . The battalion 's normal complement of 600 men was supported by a section of sappers from the Royal Engineers , eight <unk> <unk> glider loads transporting <unk> and trailers , and stores including explosives , an anti @-@ tank gun and <unk> . Three of the gliders , transporting 50 volunteers , were to carry out a coup de main landing onto the position to coincide with the ground assault . In April 1944 , the force was taken to <unk> Hill in Berkshire , where over seven days the Royal Engineers had built a full @-@ scale replica of the battery , including obstacles and barbed wire fences . The following five days were spent holding briefings and getting acquainted with the layout of the battery . They carried out nine practice assaults , four of them at night . Due to the nature of the mission , the battalion was given additional medical support from No. 3 Section <unk> ( Parachute ) Field Ambulance . Another unit that would be present during the attack but not directly involved was A Company of the 1st Canadian Parachute Battalion . This company was tasked to provide covering fire for the 9th Battalion 's approach to and withdrawal from the battery . The assault had to be completed and the battalion clear of the position by 05 : 00 , when the Royal Navy cruiser HMS <unk> would open fire on the battery in an attempt to destroy it with naval gunfire . 
