Operation TUMBLER-SNAPPER

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 at 800-462-3683.

Operation TUMBLER-SNAPPER, a series of atmospheric nuclear tests, was conducted by the Atomic Energy 

Commission (AEC) at the Nevada Proving Ground (NPG) from April 1 to June 20, 1952. The operation 

consisted of eight nuclear detonations in two phases. The TUMBLER phase, of primary concern to the 

Department of Defense (DOD), consisted of four weapons effects tests, Shots ABLE, BAKER, CHARLIE, and 

DOG. These airdropped devices were detonated to collect information on the effect of the height of burst on 

overpressure. Shots CHARLIE and DOG were also part of the SNAPPER phase, of primary concern to the 

AEC and the Los Alamos Scientific Laboratory. The other weapons development tests in the SNAPPER phase 

were Shots EASY, FOX, GEORGE, and HOW. The primary purpose of these four tower shots was to gather 

information on nuclear phenomena to improve the design of nuclear weapons.

Historical Background

About 7,400 of the estimated 11,700 DOD participants in TUMBLER-SNAPPER took part in Exercise Desert 

Rock IV. The remaining DOD personnel assisted in scientific experiments, air support activities, or 

administration and support activities at the NPG.

Exercise Desert Rock IV, an Army training program involving personnel from the armed services, included 

observer programs and tactical maneuvers. Observer programs, conducted at Shots CHARLIE, DOG, FOX, 

and GEORGE, generally involved briefings on the effects of nuclear weapons, observation of a nuclear 

detonation, and a subsequent tour of a display of military equipment exposed to the detonation. Tactical 

maneuvers, conducted after Shots CHARLIE, DOG, and GEORGE, were designed both to train troops and to 

test military tactics. Psychological tests were conducted at Shots CHARLIE, FOX, and GEORGE to determine 

the troops' reactions to witnessing a nuclear detonation.

Soldiers from various Sixth Army units provided support for the Exercise Desert Rock IV programs. They 

maintained and operated Camp Desert Rock, a Sixth Army installation located 3 kilometers (1.9 miles) south of 

the NPG. These soldiers provided essential services such as food, housing, transportation, communications, 

construction, and security. Some of the Desert Rock support troops worked in the forward areas of the NPG to 

construct observer trenches, lay communication lines, provide transportation, and assist with other 

preparations for Desert Rock IV activities. Many of the Camp Desert Rock support personnel observed at 

least one detonation during TUMBLER-SNAPPER, and some were called upon to perform support or staff 

duties in the test areas during nuclear detonations.

DOD personnel also participated in scientific experiments conducted by two test groups at TUMBLERSNAPPER: the Military Effects Test Group and the Weapons Development Test Group. The Military Effects 

Test Group was sponsored by Test Command, Armed Forces Special Weapons Project (AFSWP), and 
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involved more DOD participants than did the AEC Weapons Development Test Group. The Los Alamos 

Scientific Laboratory conducted most of the Weapons Development Test Group activities, but DOD personnel 

were sometimes involved. Test group participants placed instruments and equipment around ground zero in 

the days and weeks before the scheduled nuclear test. After each detonation, when it was determined that the 

area was radiologically safe for limited access, these participants returned to the test area to recover 

equipment and gather data.

DOD personnel also provided air support to TUMBLER-SNAPPER. The Air Force Special Weapons Center 

(AFSWC) from Kirtland Air Force Base, New Mexico, had primary responsibility for cloud sampling, courier 

missions, cloud tracking, aerial surveys of the terrain, and other air support as requested. AFSWC consisted of 

units of the 4925th Test Group and 4901st Support Wing, which staged out of Indian Springs Air Force Base, 

Nevada.

Although the AEC Test Manager was responsible for planning, coordinating, and executing TUMBLERSNAPPER programs and activities, DOD personnel assisted in these duties. They were responsible for 

overseeing the DOD technical and military operations at the tests.

Summaries of Operation TUMBLER-SNAPPER Nuclear Weapons Tests

The eight TUMBLER-SNAPPER tests are summarized in the accompanying table. The accompanying map 

shows the ground zeros of these shots.

Shot ABLE, an airdropped device, was detonated 793 feet over Area 5 of Frenchman Flat at 9 a.m. on April 1, 

1952. The test was a weapons effects test and involved DOD personnel from the Military Effects Test Group

and the Weapons Development Test Group in about 30 scientific and diagnostic experiments. AFSWC 

activities included the airdrop, cloud sampling, courier service, cloud tracking, and aerial surveys. In addition, 

over 150 personnel from the Strategic Air Command (SAC) observed the detonation from B-50 aircraft flying 

over the test area. No formal military training exercises were conducted at this shot, although 15 members of 

the Camp Desert Rock support staff witnessed the shot near the Control Point, approximately 18 kilometers

(11.2 miles) northwest of ground zero. Onsite radiation intensities were characterized by small areas of lowlevel radioactivity surrounding ground zero. Six hours after the shot, radiation intensities were below 

0.01 roentgen per hour (R/h) beyond about 600 meters (0.4 miles) from ground zero.

Shot BAKER, an airdropped device, was detonated 1,109 feet over Area 7 of Yucca Flat at 9:30 a.m. on 

April 15, 1952. Shot BAKER was also a weapons effects test and involved DOD personnel from the test 

groups in 45 experiments. AFSWC activities included the airdrop, cloud sampling, courier service, cloud 

tracking, and aerial surveys. About 170 SAC observers flying in B-50 aircraft witnessed the detonation. No 

formal military training exercises were conducted, but 10 members of the Camp Desert Rock staff did witness 

the shot. Onsite radioactivity was characterized by small areas of radiation around ground zero. About one 

hour after the shot, the initial radiological survey team found a radiation intensity of 1.2 R/h at ground zero, 

decreasing to 0.01 R/h 750 meters south of ground zero.

Shot CHARLIE, an airdropped device, was detonated about 3,500 feet over Area 7 of Yucca Flat at 9:30 a.m. 

on April 22, 1952. About one hour after the shot, the initial survey showed that radiation intensities of 0.01 R/h 

or more were confined within 1 kilometer (0.6 mile) of ground zero.

As part of Exercise Desert Rock IV, the armed services fielded a troop observer program with 535 participants 

and a tactical troop maneuver with about 1,675 participants. The tactical maneuver at Shot CHARLIE was 

conducted by the following units:
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Army

• 2nd Battalion, 504th Airborne Infantry Regiment, 82nd Airborne Division, Fort Bragg, North Carolina

• Company B, 167th Infantry Regiment, 31st Infantry Division, Camp Atterbury, Indiana

• Company C, 135th Infantry Regiment, 47th Infantry Division, Fort Rucker, Alabama

• Tank Platoon, 11th Armored Cavalry Regiment, Camp Carson, Colorado

• Engineer Platoon, 369th Engineer Amphibious Support Regiment, Fort Worden, Washington

• Medical Detachment (augmented), Sixth Army, numerous Sixth Army posts.

Air Force

• 140th Fighter-Bomber Group (Provisional) and elements from 140th Fighter-Bomber Wing, Clovis Air 

Force Base, New Mexico.

The CHARLIE tactical maneuver consisted of five activities:

• Observation of the shot

• Psychological testing

• Movement to objective

• Inspection of an equipment display

• Airborne exercise.

After observing the shot from trenches approximately 6.4 kilometers (4 miles) south of ground zero, the troops 

were tested by the Human Resources Research Office and the Operations Research Office to determine their 

reactions to the detonation. The troops then toured the display area and approached as close as 160 meters 

to ground zero, where they encountered radiation intensities of up to 0.01 R/h. While ground troops were 

taking part in these activities, Army paratroopers landed in a drop zone north of ground zero. Some of the 

paratroopers, however, jumped prematurely and missed the drop zone by as much as 13 kilometers (8 miles). 

Five paratroopers were slightly injured on landing. Despite this problem, the exercise was completed as 

planned.

In addition to Exercise Desert Rock activities, DOD personnel participated in about 50 scientific projects, 

approximately 190 SAC observers witnessed the shot from aircraft flying in the vicinity of the NPG, and 

AFSWC personnel provided air support, including the bomb drop.

Shot DOG, an airdropped device, was detonated more than 1,000 feet above Area 7 at 8:30 a.m. on 

May 1, 1952. Ground zero for Shot DOG was the same as for Shots BAKER and CHARLIE. The initial 

radiation survey, taken about one hour after the shot, showed that radiation intensities of 0.01 R/h extended 

approximately 1.6 kilometers (1 mile) from ground zero.

The Navy and Marine Corps conducted a troop observer program and a tactical troop maneuver at Shot DOG 

as part of Exercise Desert Rock IV. The observer program involved approximately 350 Navy and Marine 

participants. Desert Rock participants observed the shot from trenches 6.4 kilometers (4 miles) south of 

ground zero. The tactical maneuver was conducted by about 1,950 Marines from the Marine Corps Provisional 

Atomic Exercise Unit. This unit consisted of officers and enlisted men from the 1st Provisional Marine 

Battalion of Camp Pendleton, California, and the 2nd Provisional Marine Battalion of Camp Lejeune, North 

Carolina. The Shot DOG tactical maneuver was the first maneuver conducted by the Marine Corps during 

continental nuclear weapons testing. The Marines observed the shot, took psychological tests, and toured 

display areas 2 hours and 20 minutes after the detonation. In addition, some participants accompanied 

AFSWP and Desert Rock monitoring teams on their initial survey of the ground zero area immediately following 

the detonation in order to learn radiological monitoring techniques. At Shot DOG, three display areas were 
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established between 270 and 1,600 meters (0.17 – 1 mile) from ground zero. The Marines stopped their tour 

of the displays at 820 meters from ground zero because of the radiation intensities they encountered.

In addition to Desert Rock activities, DOD personnel participated in about 50 of the scientific experiments 

conducted by the test groups, about 180 observers from the SAC watched the detonation from aircraft flying in 

the vicinity of the NPG, and AFSWC personnel provided air support, including the bomb drop.

Shot EASY was detonated from a 300-foot tower in Area 1 of Yucca Flat at 4:15 a.m. on May 7, 1952. DOD

participants were involved in approximately 30 of the test group experiments, and AFSWC personnel provided 

air support. No formal Desert Rock IV training exercises were conducted. However, 1,000 personnel from 

Camp Desert Rock support units witnessed the shot from the Control Point at Yucca Pass, approximately 

13 kilometers (8 miles) south of ground zero. Onsite residual radioactivity was heaviest around and to the 

north of ground zero. The initial radiological survey team was unable to complete the survey on shot day 

because of the large radiation area and rough terrain. On the day after the shot, the 0.01 R/h line was 900 to 

1 kilometer (6.2 miles) east, south, and west of ground zero but extended about 6 kilometers (3.7 miles) north.

Shot FOX, a 300-foot tower detonation, was fired in Area 4 of Yucca Flat at 4 a.m. on May 25, 1952. Most 

onsite fallout occurred to the northeast of ground zero, overlapping residual radiation from Shot EASY. Ninety 

minutes after the shot, the 0.01 R/h line extended farther than 6.5 kilometers to the east. High radiation levels 

to the northeast prevented completion of the initial radiological survey on shot day. Three days after the shot, 

the 1.0 R/h line extended less than 500 meters (0.3 miles) from ground zero, except to the northeast where it 

reached nearly 2 kilometers (1.2 miles).

During Shot FOX, the largest single activity was the Army troop observer program, part of Exercise Desert 

Rock IV. Approximately 950 exercise troops from the 701st Armored Infantry Battalion, 1st Armored Division, 

Fort Hood, Texas, witnessed the shot from trenches 6.4 kilometers (4 miles) southeast of ground zero. An 

additional 500 observers from the six continental armies and the service schools also witnessed the shot from 

the same location. The observer program included psychological testing before and after the shot and a tour 

of the equipment display area.

In addition, DOD personnel were involved in 27 test group experiments. AFSWC personnel provided air 

support, and about 100 observers from the SAC witnessed the shot from aircraft flying in the vicinity of the 

NPG.

Shot GEORGE, a 300-foot tower detonation in Area 3, was fired at 3:55 a.m. on June 1, 1952. The initial 

radiation survey established the 0.01 R/h line at about 1.3 kilometers (0.8 miles) to the west, south, and east of 

ground zero. The area north of the shot tower could not be surveyed on shot day because of radiation levels 

in excess of 10.0 R/h.

The Desert Rock troop observer program and tactical troop maneuver at Shot GEORGE involved 

approximately 1,800 Army troops. Immediately after they observed the shot from trenches about 

6.4 kilometers (4 miles) south of ground zero, about 500 soldiers toured the equipment display area, located 

about 500 to 2,500 meters (0.3 to 1.6 miles) southwest of ground zero. The remaining 1,300 soldiers took part 

in the tactical troop maneuver, a ground assault on an objective south of ground zero. Immediately after the 

shot, the troops, accompanied by five tanks, advanced from the trench area toward the objective. When Army 

monitors preceding the assault detected radiation intensities of 0.5 R/h at about 460 meters (0.3 miles) from 

ground zero, the attack was halted. Troops then proceeded to the equipment display areas. The following 

Army units took part in this maneuver:

• 23rd Transportation Truck Company, Camp Roberts, California

• 31st Transportation Truck Company, Fort Ord, California
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• Tank Platoon of the 1st Armored Division, Fort Hood, Texas

• 369th Engineer Amphibious Support Regiment, Fort Worden, Washington.

In addition to these Desert Rock activities, DOD personnel participated in 25 of the test group projects, 

AFSWC personnel performed air support missions, and 24 observers from the SAC watched the detonation 

from two B-50s flying in the vicinity of the NPG.

Shot HOW, the last test of the operation, was detonated from a 300-foot tower in Area 2 of Yucca Flat at 

3:55 a.m. on June 5, 1952. No Exercise Desert Rock programs were conducted, but DOD personnel did 

participate in about 30 of the test group projects. The onsite fallout pattern extended to the north and 

northwest of ground zero, but the initial radiological survey team did not monitor that area because no recovery 

operations were necessary there. The survey team did measure intensities of 0.01 R/h as far as 2 kilometers 

(1.2 miles) to the west of ground zero.

Radiation Protection Standards

The AEC established safety criteria to minimize the exposure of participants to ionizing radiation while allowing 

them to accomplish their missions. The AEC established a limit of 3.0 roentgens (R) of gamma exposure per 

13-week period for Exercise Desert Rock, the joint AEC-DOD organization, and most of AFSWC. AFSWC 

sampling pilots were authorized to receive up to 3.9 R during TUMBLER-SNAPPER because their mission 

required them to penetrate the clouds formed by the detonations.

The Test Manager was ultimately responsible for the safety of participants in Exercise Desert Rock IV, of the 

personnel in the joint AEC-DOD organization, and of individuals residing within 320 kilometers of the NPG. 

Most onsite and offsite radiological safety procedures were performed by the AFSWP Radiological Safety 

Group, composed of personnel from the Army, Navy, and Air Force. An officer appointed by Test Command, 

AFSWP, headed the group.

The Desert Rock Exercise Director was responsible for conducting Exercise Desert Rock IV in compliance with 

the AEC radiological safety policies. The Desert Rock Radiological Safety Group was usually supervised and 

assisted by the AFSWP Radiological Safety Group. The AFSWP group was also responsible for processing 

the film badges worn by Desert Rock participants.

The 4925th Test Group (Atomic) implemented radiological safety procedures for AFSWC personnel at Indian 

Springs Air Force Base. For AFSWC personnel at Kirtland Air Force Base, the 4901st Support Wing (Atomic) 

carried out these procedures.

Although the missions and activities of each organization were different, the general radiological safety 

procedures followed by all groups were similar:

• Orientation and training – preparing radiological monitors for their work and familiarizing participants 

with radiological safety procedures

• Personnel dosimetry – issuing and developing film badges and evaluating gamma radiation exposures 

recorded on film badges

• Use of protective equipment – providing clothing, respirators, and other protective equipment

• Monitoring – performing radiological surveys and controlling access to radiation areas

• Briefing – informing observers and project personnel of radiological hazards and the radiological 

conditions in the test area

• Decontamination – detecting and removing contamination from personnel and equipment.
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Radiation Doses at Operation TUMBLER-SNAPPER

The AEC established a limit of 3.0 rem∗ of gamma dose per 13-week period for Exercise Desert Rock 

personnel, for the joint AEC-DOD organization and for most AFSWC personnel. AFSWC sampling pilots were 

authorized to receive up to 3.9 rem during TUMBLER-SNAPPER in order to complete their scientifically vital 

mission.

Individual film badges were generally worn during missions in contaminated portions of the forward area, but 

dosimetry records are only partially available. Notably, the disposition of film badges issued to the Marine 

Corps Provisional Atomic Exercise Unit at Shot DOG has never been determined. Operational total doses are 

available for personnel based at Camp Mercury, and doses to Desert Rock IV personnel whose records are 

not available have been reconstructed.

About 40 DOD participants who were subject to the joint AEC-DOD organization limit of 3.0 rem exceeded it, 

and about 10 individuals subject to the 3.9 rem AFSWC limit received doses in excess of that level. The 

highest doses of about 10 rem were accrued by two members of the Army unit that assisted the AEC in 

radiological monitoring, the 216th Chemical Service Company. The highest AFSWC dose was less than 

8 rem. Desert Rock IV personnel remained within their dose limit.

Some DOD personnel assisting the Military Effects Group received doses over the limits because the nature of 

their experiments required them to enter radiation areas before the recovery hour to retrieve instruments and 

records, or to remain in the radioactive areas longer than originally anticipated.

At Shot DOG, which had higher levels of radiation than did the previous three shots, 15 AFSWP participants 

received doses greater than 3.0 rem. At Shot FOX, Project 6.4 required flying repeatedly through the cloud, 

with peak intensity readings of as much as 40 R/h.

During Shot GEORGE, a T-33 flew through a highly radioactive part of the cloud while performing its cloud 

sampling mission. The plane reported a radiation intensity of 140 R/h and returned to base. Shot GEORGE 

produced more fallout than expected in the target area, resulting in “unusually extensive” decontamination 

activities. Six AFSWP participants received doses over 3.0 rem.

The totals of reconstructed and film badge doses for DOD participants at TUMBLER-SNAPPER are depicted 

below.

 ∗ A rem is a radiation protection unit of measure that quantifies the risk of biological effects resulting from exposure to 

ionizing radiation. Ionizing radiation is any radiation (gamma, x-ray, beta, neutron, or alpha) capable of displacing 

electrons from atoms or molecules, thereby producing ions. According to the National Council on Radiation Protection 

and Measurements (NCRP, Report No. 160, Table 1.1), the general U.S. population receives about 0.62 rem per year 

from natural background radiation sources (radon, cosmic rays, and rocks) and man-made radiation sources (medical 

diagnostic x-rays and consumer products). As a basis of comparison, a standard diagnostic chest x-ray delivers a 

radiation dose of about 0.02 rem.
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For more information on reconstructed doses, see the report “Analysis of Radiation Exposure for Observers 

and Maneuver Troops, Exercise Desert Rock IV, Operation TUMBLER-SNAPPER” (DNA-TR-85-277). Also 

see the report “Operation TUMBLER-SNAPPER 1952” (DNA 6019F). These reports are available online at 

http://www.dtra.mil/DTRA-Mission/Reference-Documents/NTPR-info/.

September 2021
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Summary of Operation TUMBLER-SNAPPER Nuclear Weapons Tests (1952)a

SHOT ABLE BAKER CHARLIE DOG EASY FOX GEORGE HOW

Sponsor DOD-LASL DOD-LASL DOD-LASL DODLASL LASL LASL LASL LASL

Planned Date Apr 1 Apr 15 Apr 22 Apr 29 May 6 May 13 May 20 May 27

Actual Date Apr 1 Apr 15 Apr 22 May 1 May 7 May 25 Jun 1 Jun 5

Time

(Pacific Standard) 9 a.m. 9:30 a.m. 9:30 a.m.

8:30

a.m.

4:15

a.m.

4 a.m. 3:55 a.m.

3:55

a.m.

NPG Location

Frenchman

Lake

(Area 5)

Area 7 Area 7 Area 7 Area 1 Area 4 Area 3 Area 2

Type of 

Detonation Airdrop Airdrop Airdrop Airdrop Tower Tower Tower Tower

Height of Burst 

(Feet)b 793 1,109 3,447 1,040 300 300 300 300

Yield

(kilotons)c 1 1 31 19 12 11 15 14

a Source: United States Nuclear Tests, July 1945 through September 1992, DOE/NV-209 (Rev. 15), Dec 2000. b Altitudes are measured from mean sea level, while heights are measured from the ground. All vertical distances are in 

feet.

c One kiloton equals the approximate energy release of one thousand tons of TNT.
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