Summary of External Doses for Operation UPSHOT-KNOTHOLE as of 1 May 1986 Gamma Dose (rem) 0-0.5 0.5-1 1-3 Army 3,705 3,041 4,459 1,299 20 Navy 402 171 96 87 16 1,125 226 260 45 17 112 205 330 11,611 16 98 28 28 2 0 Air Force Marine Corps Civilian DOD Participants 4.10 3-5 5-10 10+ 10 0 OPERATION CASTLE. CASTLE was conducted at Enewetak and Bikini Atolls during the spring of 1954. The first event of this series, Shot BRAVO, had a yield of 15 megatons and was the largest device ever detonated by the U.S. Government as part of atmospheric nuclear weapons testing. The following table provides specifics on this detonation, shown in figure 13 (F), as well as the other five in the series (13: 1): Event BRAVO 1 March ROMEO 27 March KOON 7 April UNION 4.10.1 Date Type Surface 15 megatons Barge 11 megatons Surface 26 April Yield 110 kilotons Barge 6.9 megatons 13.5 megatons YANKEE 5 May Barge NECTAR 14 May Barge 1.69 megatons Background and Objectives of Operation CASTLE. CASTLE was the culmination in the development of the super, or hydrogen, bomb that began in 1950. Shot GEORGE, a test in the 1951 GREENHOUSE series, had demonstrated the initiation of a sustained thermonuclear reaction by use of a fission reaction. Fusion, or thermonuclear, reactions had been used in 103