A number of XW-51 / XW-54 tests followed in the 1958 Operation Hardtack II test series , including Hardtack II Otero , Bernalillo , Luna , Mora , Colfax , Lea , Hamilton , Dona Ana , San Juan , Socorro , Catron , De Baca , Chavez , Humboldt , and Santa Fe . By this time , the XW-51 / XW-54 design had been test-fired more times than any preceding US nuclear weapon prior to its successful introduction in service , indicating the difficulty of successfully making this small and low-yield design work reliably and safely
Operation Hardtack II
Operation Hardtack II
W54