Note: For information related to claims, call the Department of Veterans Affairs (VA) at 800-827-
1000 or the Department of Justice (DOJ) at 800-729-7327. For all other information, call the
Nuclear Test Personnel Review (NTPR) Program Helpline at 800-462-3683.
Operation CASTLE was a six-detonation nuclear weapon test series (see table below) held at the
Atomic Energy Commission’s (AEC) Pacific Proving Ground (PPG) in 1954. The PPG consisted
principally of Enewetak and Bikini Atolls in the northwestern Marshall Islands in the Central Pacific
The CASTLE series was held to test large-yield thermonuclear, or hydrogen, devices. Work on this
class of devices had progressed through the GREENHOUSE-GEORGE demonstration shot in 1951
and the IVY-MIKE shot of 1952. MIKE was the first device that generated substantial explosive
energy from the fusion, or joining, of hydrogen atoms. These explosive devices were developed by
the AEC, the civilian agency authorized to perform this activity by the Atomic Energy Act of 1946.
The devices were tested at the PPG by a joint military and civilian organization designated as Joint
Task Force 7 (JTF 7). This was a military organization in form, but was populated by military, civil
service and contractor personnel of the Department of Defense (DoD) and 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). The peak DoD numerical strength of
CASTLE was approximately 17,300 personnel.
Numerous technical demonstrations were carried out in conjunction with each of the six detonations.
These demonstrations measured the power and efficiency of the devices and attempted to gauge the
military effects of the explosions. DoD personnel participated in this test operation as individuals
whose duty stations were at the AEC design laboratories, as units performing separate
demonstrations, and as units