Given that the role of helicopters in land force operations was increasing, as was the integration of guided missile destroyers for coastal defence, the board of inquiry recommended an amendment to NATO procedures for amphibious warfare and naval gunfire support, to alert other armed forces to the danger of underestimating a ship's missile engagement zone over land.[2] During the late 1980s, the British government placed more emphasis on joint warfare training, with exercises, such as Purple Warrior, taking place in Oman and Scotland.[2][7] The board noted the establishment of the Permanent Joint Headquarters, designed to put an end to the "ad hoc and reactive way" in which operations had been carried out while under single service control.[2][27] IFF transmitters were fitted to all Army Air Corps and Royal Marine Gazelle and Lynx helicopters,[2] and the problem of operating IFF in the vicinity of Rapier batteries was successfully addressed.[2] The board supported a recommendation that the responsibilities of naval gunfire-support liaison officers could be broadened to include the interpretation of air defence problems during inshore joint warfare operations.[2]