H.
ECHR
Defense Nuclear Agency
Public Affairs Office
Washington, D.C. 20305
S h eet
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 Hardtack 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 above 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 (JTF 7).
JIF 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).
TEST OPERATIONS
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 shots in HARDTACK large,
but the variety of types was great; land- and water-surface events, underwater detonations,
and ballon-and rocket-borne high-altitude tests were conducted.
fact sheet lists the names, dates, and locations of the shots.
The following page of this
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 mid-1950s.
In these tests, the AEC weapon development laboratories (Los Alamos 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 underwater 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 explo-
sions 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.