Operation Redwing was a United States series of 17 nuclear test detonations from May to July 1956. They were conducted at Bikini and Enewetak atolls. The entire operation followed Project 56 and preceded Project 57. The primary intention was to test new, second-generation thermonuclear devices. Also tested were fission devices intended to be used as primaries for thermonuclear weapons, and small tactical weapons for air defense. Redwing demonstrated the first US airdrop of a deliverable hydrogen bomb - test Cherokee. Because the yields for many tests at Operation Castle in 1954 were dramatically higher than predictions, Redwing was conducted using an "energy budget" - there were limits to the total amount of energy released, and the amount of fission yield was also strictly controlled.