Chapter 5 - Operational Phase Operation HARDTACK involved the detonation of some 35 nuclear devices, Of these, 11 were detonated at Eniwetok, 22 at Bikini Atoll, and two at Johnston Island. On four occasions two detonations occurred the same day and 17 occurred on successive days. in connection with the operation. A total of 257 sorties were flown The organizational structure and the resources made available to Task Group 7.4 proved adequate to meet its mission committments. Five of the events: the two underwater shots, WAHOO and UMBRELLA, and the three high altitude shots, YUCCA, TEAK and ORANGE, gave rise to some new operational problems but in each instance we were able to resolve these problems and perform the required missions. The command arrangements in the forward area were varied depending on location of events and operational requirements. z The first event was YUCCA, the high altitude balloon shot conducted at Bikini Atoll. This event imposed some unusually stringent command and operational problems. The Task Group Commander exercised command of the air operation from the Air Operations Center (AOC) in the USS BOXER. His deputy was responsible for the dispatch and recovery of test aircraft from Eniwetok. He used the Air Operations Center at FRED Island, Eniwetok Atoll, as his comzand post. On subsequent Bikini events, the Bikini Air Operations Center was under the direct on-the spot supervision of either the Task Group Commander or one of his senior officers, and the Task Group Cqmmander exercised overall contro] from the FRED AOC. The Commander of the Test Aircraft Unit was responsible for the pre and post-mission operation of aircraft on the air base. He ex- ercised this control from a radio-equipped vehicle on the ramp itself. The Flying safety Officer or a senior operations officer manned the tower during missions to assist in expediting landings and takeoffs. aS