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Naval Proving Ground at Dahlgren and the Hidden History of the VT Fuze

By Peter R. Kolakowski, Special Guest Writer

“If a secret weapon is defined as a truly effective weapon on which absolute secrecy has been maintained, then the Navy’s VT, or proximity fuze, was one of the outstanding secret weapons of the war. It is not only an amazing anti-aircraft device, but has proved equally effective in land warfare.”

—Vice Admiral George F. Hussey, Jr.

The atom bomb, radar, and the variable time (VT) fuze are considered the three major ordnance inventions of World War II. While the Naval Proving Ground at Dahlgren was involved in all three of these inventions, the least known is the VT fuze work performed on the Potomac River Range and in the Chesapeake Bay during WWII and after, even to this day.

The major individuals involved in advocating, testing, and delivering the VT fuze to the fleet, to the U.S. Army, and to the allies in WWII were also integral in bringing the other inventions to operational use. Besides the visibility of the other inventions, there was a secrecy concerning the VT fuze program that even included discussion of the program and its successes. In fact, during WWII, using the words “variable” and “proximity” in conjunction with “fuze” was classified. Thus, the term VT fuze was accepted to discuss the work among the many hundreds of people involved. The VT fuze program was not fully declassified until 1954.

The U.S. Navy had developed in 1939–1940 two new antiaircraft guns, 20mm Oerlikon and 40 mm Bofors, mainly directed by radar-equipped fire control instruments. The shells used then were the standard two types of fuzes: mechanical and percussion, which had been in existence since medieval times, 600 years earlier. Until 1942, the U.S. Navy’s Bureau of Ordnance (BUORD) annually procured 10 versions of these fuzes. By VJ [Victory in Japan] Day, 15 August 1945, BUORD was procuring 90 fuze types, the vast majority being VT fuzes.

BUORD stated the “Radio Proximity Fuze” requirements: “What was needed was a fuze that would automatically detonate a projectile when it came within destructive range of a target. A device with a self-contained source of intelligence would eliminate most of the variables in anticraft fire control.”

How did the U.S. Navy and the Naval Proving Ground at Dahlgren help develop, test, and field the VT fuze that dramatically helped win WWII? It all began with British scientist Sir Henry Tizard’s clandestine mission authorized by Prime Minister Winston Churchill and supported by President Franklin Delano Roosevelt in August 1940. The British Technical and Scientific (Tizard) Mission shared Britain’s entire military technology secrets with the U.S. government in exchange for access to America’s industrial capacity to produce weapons. Many blueprints and prototypes from research were shared, especially for radar and fuzes. The British called their VT fuze research the “Bonzo” fuze.

In August 1940, the National Defense Research Council (NDRC) directed the Navy to lead the fuze development. In turn, ADM William H. Blandy*, head of BUORD, directed the Navy Department Council for Research and the Naval Research to lead the development. The Carnegie Institution for Science was contracted by the NDRC on 17 August; one week later, Dr. Merle A. Tuve was named chair of NDRC’s Section T for the Department of Terrestrial Magnetism. In July 1941, the Navy placed focus on projectile fuze research with Section T. Section T was removed from the NDRC, then placed under Director of the Office of Scientific Research and Development, who subsequently contracted to John Hopkins University that, in turn, created the Applied Physics Laboratory (APL) in March 1942 to do continuing research. The APL considers the VT fuze work performed by Dr. Tuve and Section T one of its significant achievements. Timely decisions were made, and the sense of urgency expressed by the many in power accelerated VT fuze research and development.


 Rear Admiral William H. P. Blandy  Merle Tuve, courtesy of JHU APL

While the principle engineering work occurred in Section T, major research, testing, and validation work on many types of VT fuzes commenced at the Naval Proving Ground at Dahlgren from late 1941 to the end of WWII. The leaders at Dahlgren were Dr. L.T.E. Thompson** and (then CAPT) RADM William “Deak” S. Parsons***. Mass production of VT fuzes was authorized by VADM George F. Hussey as well as continuing research, testing and evaluation of the fuzes from 1942 to the end of the war at Dahlgren.


Dr. L.T.E Thompson RADM Deak Parsons

The Naval Proving Ground at Dahlgren involved the efforts of many civilian and military personnel in the labs and particularly on the Potomac River Range. Although their names are unknown, their work comprised the research, test, and validation required for fielding the VT fuze. Feasibility work began 29 January 1942 with VT pilot fuzes fired on 5" projectiles on the Potomac River Range over a five-mile trajectory.

In April 1942, firing VT fuzed projectiles at real targets was suspended because feasibility was proved. Production contracts were let to the Crosley Corporation, which became the lead contractor for VT fuze production. The testing of the production pilot VT fuzes showed a 70% success rate. Rare footage of test firing VT fuzes at the Potomac River Range can be found at 

USS Cleveland conducted pre-combat VT fuze test firing on 12 August 1942 in the mouth of the Chesapeake Bay. Three radio-controlled targets (now called drones) were flown at the light cruiser for a three-day test of the antiaircraft defense. The lead class ship, USS Cleveland, had a 90% new recruit and 10% seasoned crew for firing antiaircraft and VT fuzes under simulated battle conditions. All three targets were destroyed on the first day by firing four VT-fuzed projectile bursts. The researchers were criticized for wasting two days’ use of a combat ship.

Subsequently, specifications for the battle VT fuze were completed and contracts let for mass production. They were transported to the Ammunition Depot at Mare Island, California, for assembly on projectiles. VADM Hussey took the risk and authorized the contracts worth $85M for the first production. Mare Island shipped the first 5,000 rounds for the Pacific Fleet’s use in combat.

On 5 January 1943, USS Helena’s aft 5" battery shot down a Japanese dive bomber with the second of three salvos of VT fuzed shells near Guadalcanal in the Solomon Islands. RADM (CAPT) Parsons was on board to witness and verify the effectiveness of VT fuzed antiaircraft fire. From this point forward, VT fuzes continued to show effectiveness in downing enemy aircraft and saving lives, especially from kamikaze attacks. By the end of the war, VT fuzed antiaircraft fire sustained a 70% success rate.

Of the Antiaircraft Fuze Battery’s rounds fired at the Potomac River Range from 1942–1945, 50% were for testing and validating VT fuzes. This equates to average weekly firing in 1942: 600 rounds; 1943: 1,650; 1944: 1,800; and 1945: 2,375. The Potomac River Range worked 24 hours a day, seven days a week during the war.

Dahlgren also participated in other significant VT fuze uses. In June 1944, the Joint Chiefs of Staff required the sharing of VT fuzes with ground forces, including the U.S. and British armies and the U.S. Marines. The deployment of antiaircraft projectiles with VT fuzes effectively neutralized the Nazi V1 and V2 rocket attacks against London and Antwerp in the fall of 1944 by eventually shooting down over 90% of the rockets.

The use of VT fuzed artillery allowed the U.S. Army to more effectively defend Bastogne and eventually win the Battle of the Bulge in December 1944–January 1945. GEN George Patton wrote: “The funny fuze {what he called the proximity fuze} won the Battle of the Bulge for us. I think that when all the armies get this shell we will have to devise some new method of warfare.”

Eventually 112 companies all over the United States were involved in producing over 70 types of VT fuzes. By the end of WWII, 22 million VT fuzes were produced. Of that amount 1.8 million were for testing. Daily, samples from each lot of fuzes were flown up to 3,000 miles to Dahlgren for the required daily quality verification tests. The cost per fuze went from $732 in 1942 to $18 in 1945. The production cost for the 22 million fuzes was $1B in 1945.

The success of the VT or Proximity Fuze program can be summarized by the following:

  • “The story of the VT fuze is a romance of science. And for three reasons it is a romance with a happy ending: first, secrecy has been effectively maintained; second, the fuze was perfected by the time it was most needed; third, the fuze actually did the job it was designed to do.”—ADM Blandy

  • The development, testing, and fielding of the VT fuze was a collaboration of the government, universities, and private sectors. The U.S. Navy had the lead role with its civilian and military leadership making the government, academic. and manufacturing sectors collaborate very well together.

Though little known, the Naval Proving Ground at Dahlgren had a critical role in the success of the VT fuze program. VT (proximity) fuze research, development. and testing continues to this day in many places, including the Naval Surface Warfare Center, Dahlgren Division.

* Blandy Road is named for ADM Blandy. As one of the heads of BUORD in WWII (VADM Hussey the other), Blandy was instrumental in providing the link of civilian and military work at Dahlgren. His steadfast support of Dr. Tuve, Dr. Thompson, and Deak Parsons allowed VT fuze work to succeed.

** Thompson Road is named for Dr. L.T.E. Thompson. He began working at Dahlgren in 1923, and pioneered the scientific research of gunnery throughout the 1930s. His metallurgical and gunnery formulae are still in use today. Leaving Dahlgren in 1943, Thompson worked the Manhattan Project and went on to further his reputation and work by setting the standard of the civilian, military, academic, and industry partnerships at China Lake, California, after World War II. See the China Lake website for his mark on this nation’s history.

*** RADM Parsons spent a number of years at Dahlgren. He left in 1943 to become part of the Manhattan Project and is better known for arming the first atomic bomb. Parsons recalls his military service at Dahlgren as enjoying living in base housing. The quarters Parsons and his family occupied still stand today.

Further reading: The Deadly Fuze: The Secret Weapon of World War II, by Ralph B Baldwin

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