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Fact Sheet – Page 1

Courtesy of MM2 Dick Lund (56-60)


Subject: HARDTACK Fact Sheet

HARDTACK was the designation given to the atmospheric nuclear weapon tests conducted by the United States in the Pacific Ocean and in Nevada in 1958. Operation Harrdtack I was a series of 35 tests, all but two of which were detonated at Enewetak* and Bikini atolls in the Marshall Islands, the Atomic Energy Commission’s (AEC) “Eniwetok Proving Ground” (EPG). The other two were detonations at 42 and 76 km about Johnston Island, which lies about 700 nmi (1,296 km) west-southwest of the Hawaiian Islands

The tests were conducted by a joint military and civilian organization, designated Joint Task Force 7 (JTF7). JTF 7 was a military organization in form but was made up of military personnel, Federal civilian employees, and contractors of the Department of Defense (DOD) and the AEC. The commander of this force was the appointed representative of the AEC and reported also to the Joint Chiefs of Staff (JCS) and the Commander in Chief, Pacific (CINCPAC).


During HARDTACK the United States fired as many nuclear devices (35) as had been fired in all prior Pacific Ocean tests. Not only was the total number of shotes in HARDTACK large, but the variety of types was great; land-and-water-surface events, underwater detonations, and balloon-and rocket-borne high-altitude tests were conducted. The following page of this fact sheet lists the names, dates, and locations of the shots.

In a sense, HARDTACK was divided into three parts. The first was aimed at the development of nuclear weapons, continuing the type of testing that had taken place at Enewetak and Bikini during the early and min-1950’s. In these tests, the AEC weapon development laboratories (Los Alomos Scientific Laboratory and the University of California Radiation Laboratory) detonated their experimental devices, with the DOD providing support and conducting experiments that did not interfere with the AEC activities.

The second part, sponsored by DOD, consisted of the underwatrer test shots, WAHOO and UMBRELLA, the first in the open ocean and the second within the lagoon at Enewetak. the purpose of these tests was to improve the understanding of the effects of underwater explosions on Navy ships and material. These tests could be considered as a continuation of BAKER test of the CROSSROADS series at Bikini in 1946 and the WIGWAM test 500 nmi (927 km) off the U.S. west coast in 1955.

* Formerly Eniwetok. The spelling of Marshall Island place names has changed in recent years in order to more accurately render the sounds of the Marshall Island names using English spelling.

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