Operation HARDTACK I Nuclear Events, 1958 (Continued) 4.15.1 Event Date Type Yield POPLAR 12 July Barge NA PISONIA 18 July Barge NA JUNIPER 22 July Barge NA OLIVE 23 July Barge NA PINE 27 July Barge NA TEAK 31 July High Altitude (Rocket) megaton range Surface NA QUINCE 6 August ORANGE 11 August High Altitude megaton range FIG 18 August Surface NA (Rocket) Background and Objectives of Operation HARDTACK I. HARDTACK I consisted of three parts. The first, aimed at the development of nuclear weapons, continued the type of testing that had been conducted at Enewetak and Bikini during the early and mid-1950s. The AEC weapon development laboratories (LANL and LLNL) detonated experimental devices, with the DOD providing support and conducting experiments that did not interfere with AEC activities (19: 1). The second part, sponsored by DOD, consisted of the underwater test shots, WAHOO and UMBRELLA, the first in open ocean and the second within the lagoon at Enewetak. These tests, which furthered efforts undertaken with the 1946 CROSSROADS and the 1955 WIGWAM series, were designed to gain additional data on the effects of underwater explosions on Navy ships and material (19: 1). The third part, sponsored by DOD, addressed a military problem that was newer: nuclear weapons in air and ballistic missile defense. 121 Shots YUCCA,