Tiny Miracle—The Proximity Fuze (2024)

By Midshipman Second Class Cameron D. Collier, U.S. Navy

Late in 1944, as General George Patton’s Third Army was moving toward Germany, he wrote a letter to the War Department describing the success his troops had experienced with a new artillery shell and fuze:

The new shell with the funny fuze is devastating. We caught a German battalion, which was trying to get across the Sauer River, with a battalion concentration and killed by actual count 702. I think that when all armies get this shell we will have to devise some new method of warfare. I am glad that you all thought of it first. 1

The idea of a target-influenced fuze was not new; similar fuzes for bombs and rockets existed at the outbreak of World War II.2 But it was a fuze rugged enough to be fired from field artillery and antiaircraft weapons that had prompted Patton’s letter. The fuze, developed largely by the Department of the Navy, has had significant effects on U.S. combat capabilities.

The proximity fuze functions as a small radio station in the shell’s nose. The basic components are a vacuum tube (six inches long and three inches in diameter) a battery, and a radio transmitter and receiver; a small glass tube filled with electrolyte solution acts as the battery. After the shell is fired and begins rotating, centrifugal force pushes the solution to the outside of the tube, where a chemical reaction occurs with small pieces of metal surrounding the tube. This produces an electrical charge which in turn arms the shell and sends out a radio impulse traveling at the speed of light. The return signal, reflected from the target, detonates the shell prior to impact and produces the devastating effects.

Shells with proximity fuzes do not need to be set to a fixed time, which makes them far more effective than conventional time and contact fuzes.3

The Germans had been working on the concept as early as 1930; by 1939, the British were involved in research.4It was the Americans, however, who did not begin research until 1940, who nearly perfected the proximity fuze.5 Responding to the spreading war in Europe and the fall of France, the National Defense Research Council (NDRC) was formed on 27 June 1940 to strengthen military research. Meetings between the NDRC and the Navy Department Council for Research headed by Rear Admiral H. G. Bowen, U.S. Navy, soon followed. The meetings focused on the growing threat of airplanes to surface ships, specifically in the Pacific; improved antiaircraft weaponry was crucial. Representatives for each group, Captain Gilbert C. Hoover of the Navy and Dr. R. C. Tolman and Dr. C. C. Lauritsen of the NDRC, met to discuss recent developments. Information on British work on proximity fuzes for use in bombs and rockets led to discussion of such a fuze for ship-based antiaircraft guns.6 [The term AAA—antiaircraft artillery—commonly describes these weapons whether afloat or ashore.]

On 12 August 1940, Captain Hoover, speaking for the Bureau of Ordnance, requested that the NDRC begin work on “rugged” proximity fuzes with directional capabilities that also could withstand the immense forces exerted by AAA.7 The term directional meant that the shell fragments would be directed toward the target. Hoover had asked for a lot, but the Council was up to the task.

A special group, Section T, began work on the project at the Carnegie Institution of Washington’s Department of Terrestrial Magnetism.8 The Department of the Navy’s role was supervisory. Rear Admiral W. H. P. Blandy, U.S. Navy, Chief of the Bureau of Ordnance, wrote in a memorandum: “The ‘how’ was left entirely to NDRC. My attitude was: ‘Here is something the Navy badly needs. Please go and get it for us. The field is wide open. We don’t know how you are going to do it. If we did—we’d have done it!”’ Trading information with the United Kingdom, Section T scientists learned that the British had devised a fuze using radio as the influence source for use in bombs and rockets. The British fuze could withstand only 100 Gs, however, far less than the 20,000 Gs required for use in a AAA projectile spinning at 28,000 revolutions per minute. The Americans took the lead, but followed British practice in using a radio transmitter and receiver as the influence medium rather than acoustical, terminal, electrostatic, magnetic, or photoelectric sensors. This proved to be the best choice.9

After the basic design characteristics of battery power, radio frequency transmitter and receiver, small size, and rugged construction had been agreed upon, Section T began rapid research. On 17 July 1941, the section split into two elements—T and E.10 Section T worked with the Navy to develop AAA fuzes, while Section E worked with the Army to develop fuzes for bombs and rockets." (What later became the U.S. Air Force was still part of the Army.)

The government then contracted with Johns Hopkins University to oversee the research.12 The University’s Applied Physics Laboratory hired 700 people; by January 1945, 26 contractors and 10,000 people were involved.13

The proximity fuze project had a top secret security classification, and clearances took time; many civilian workers never did know what they were working on.14 The Department of the Navy received special authorization to divert men from selective service; they were either commissioned or worked as part of a special civilian team.15 In the case of Lieutenant (junior grade) C. Doyle Collier, the Navy rejected his request for sea duty, made him the engineering officer for the Aviation Ordnance Officer’s School at the Jacksonville Naval Air Station, Florida, and then sent him to Maryland to aid in the development of the proximity fuze16

At the Applied Physics Laboratory, workers tested only the smallest tubes and radios to increase the number of possible applications. The small glass tubes used to house the electrolyte solution were packaged so that they would not break under the force of gunfire. Machines—and actual firings—tested each tube to 20,000 Gs.17 In several instances, workers dropped the tubes from the third floor of the Pratt Library in Baltimore, Maryland, to test their strength.18 Researchers changed the battery from a standard dry cell battery to a wet cell battery, which provided for a longer shelf life.19

The cruiser Cleveland (CL-55) performed the first test firing of the new proximity fuze in early August 1942 in the Chesapeake Bay.20 It was a success from the start. In November 1942, the Navy sent 5,000 of the new influence fuzes to Pearl Harbor, Hawaii, where the U.S. Pacific Fleet got a total of 4,500 of them.21 War against Japanese dive bombers in the South Pacific soon changed. Fear that the Japanese might capture unexploded shells containing the fuze restricted their use to the open ocean until 1944.

The USS Helena (CL-50) is credited with the first proximity-fuzed shell kill against an enemy aircraft—a Japanese dive bomber that had just made a bombing run on the ship on 6 January 1943 off Cape Hunter on the south coast of Guadalcanal. The crew fired three shells with little time to aim, but all three exploded and downed the distant aircraft. 22 It had taken the NDRC just 30 months to accomplish what had seemed an impossible task.

Admiral Arleigh Burke, U.S. Navy (Retired), former Chief of Naval Operations, spoke of their effectiveness during a 1978 interview at the Applied Physics Laboratory:

When I went as chief of staff to [Vice] Admiral [Marc] Mitscher who commanded the Fast Carrier Task Forces, all the 5-inch/38 and 5-inch/25 ammunition was fitted with VT [proximity] fuzes and as you well know, those fuzes knocked down enemy planes by the dozens. Had it not been for those fuzes, our ship losses and casualties in the Fast Carriers in the last half of the war would have been enormously larger. . . . That fuze was a magnificent help.25

Pacific theater statistics support his statement. The proximity fuze proved three to four times more effective than conventional time fuzes, and night kill-ratios increased by 370%.24

In 1943, naval guns fired 36,370 antiaircraft rounds. Although only 25% used proximity fuzes, these accounted for 51% of the kills.25 The new shells had a lethal fragment area much larger than that of conventional fuzes—3,000 square feet as opposed to 60 square feet—a major advantage over typical time fuzes.26 The startling results led the Navy to use the fuzes 75% of the time.27

The proximity fuze contributed significantly to U.S. success in many Pacific battles, including the Battle of the Philippine Sea—“The Great Marianas Turkey Shoot.”28 After use of the fuze over land was authorized, shells fitted with it were used in many amphibious assaults, where the shell fragments devastated large areas of the beaches prior to the assaults.29

Secretary of the Navy James Forrestal put it this way:

The proximity fuze has helped blaze the trail to Japan. Without the protection this ingenious device has given the surface ships of the Fleet, our westward push could not have been so swift and the cost in men and ships would have been immeasurably greater.50

Shells with proximity fuzes were just as devastating in Europe, where they were used against ground forces as well as aircraft. The Army was the primary user; naval forces used them only occasionally in the Mediterranean. Air Force General Sam Phillips expressed his views on the use of the proximity fuze in Europe in a 1988 interview: “ . . . had the Germans perfected an effective proximity fuse, well before the war ended, the outcome of the war could significantly have been affected.”51

The United States authorized the use of proximity fuzes over land regions in defense of London against the Germans’ V-1 rockets on 12 June 1944. From the first day of the attacks to the end of August, the Germans launched 9,300 V-1s, an average of 120 per day.32 By the end of the fourth week, antiaircraft shells equipped with proximity fuzes accounted for the destruction of 79% of all incoming rockets.55 The proximity fuzes saved London. As Section T’s E. O. Slant recorded in a letter: “Actually you can be sure that the VTF [variable time fuze] has saved the lives of thousands here.”34

The fuze also aided land forces as an antipersonnel weapon during the Battle of the Bulge and afterward. Detonating at a predetermined height above ground, it spread shrapnel over large areas, causing mass destruction. One German prisoner described the attacks as being quick powerful bursts for which there was simply no defense.35 “The 8th Infantry Division caught a German patrol in the Hurtgen Forest in a Pozit TOT (position time-on-target mission). Ninety-six Germans were found. . . .”36

The fuze helped turn the tide at the Battle of the Bulge. Allied AAA accounted for the destruction of 417 German aircraft during the battle.37 The important port of Antwerp was defended by AAA using proximity fuzes. General Dwight D. Eisenhower gave a great deal of credit to the small weapon toward the end of the war:

It seemed likely that, if the German had succeeded in perfecting and using these new weapons six months earlier than he did, our invasion of Europe would have proven exceedingly difficult, perhaps impossible.38

Today, the principle is used in such major weapons as the Phoenix AIM-54 air-to-air missile, the Standard Missile (SM)-l and SM-2 surface-to-air missiles, and the Patriot surface-to-air missile—which proved an effective intercept missile during the Gulf War.39

Rarely has such a small, simple device had such a dramatic impact. The atomic bomb overshadowed much of its success, but it was a morale-booster on the battlefield— and that is not all: the project integrated talented civilian and military scientists, engineers, and technicians, and it opened lines of communication with Allied scientists, especially the British. Its legacy continues today.

Tiny Miracle—The Proximity Fuze (2024)


How effective is proximity fuze? ›

Proximity fuzes are designed for elusive military targets such as airplanes and missiles, as well as ships at sea and ground forces. This sophisticated trigger mechanism may increase lethality by 5 to 10 times compared to the common contact fuze or timed fuze.

How did the proximity fuse work? ›

The proximity fuzes developed in World War II markedly increased the effectiveness of artillery by triggering the explosion of the shell by its proximity to the target. This was accomplished by including a tiny radar-like radio sender-receiver in the fuze.

How much did the proximity fuse cost? ›

During the course of the war, the proximity fuze program as a whole cost approximately a billion dollars in contemporary money, or about $15 billion today. The cost per fuze fell from $732 in 1942 to as low as $18 in 1945, and over 22 million were produced.

What are the advantages of radio proximity fuze? ›

The advantage was that the gunners could fire shells to explode over troop positions, showering them with deadly shell fragments. The proximity fuze sensed radar returns from the ground and triggered the explosive charge while the shell was still 20 to 50 feet (6 to 15 m) in the air.

What was the smallest proximity fuze shell? ›

30″/7.62mm(ish). Although the smallest practical HE rounds start at the . 50″/12.5mm range*, which is probably the smallest round in which you could fit a proximity fuse and HE charge and not be utterly useless.

What is the difference between a fuse and a fuze? ›

FUSE: Cord or tube for the transmission of flame or explosion usually consisting of cord or rope with gunpowder or high explosive spun into it. FUZE: A device with explosive components designed to initiate a main charge. Interchangeable terms; above versions are preferred.

How did anti-aircraft shells work? ›

Anti-aircraft and other artillery rounds typically consist of an outer shell packed with a large amount of high explosives. These explosives are relatively stable, and require the activation of a fuse to detonate. Before World War II, there were two broad categories of fuses: impact and timed.

How does he vt work? ›

HE-VT rounds are an advanced round fitted with a specialised proximity fuse, designed to detonate the round upon reaching close proximity with a target. These are usually designed for anti-air applications, and are generally ineffective against most ground targets.

What is laser proximity fuze? ›

A proximity fuze is a fuze that detonates an explosive device automatically when the distance to the target becomes smaller than a predetermined value. Proximity fuzes are designed for targets such as planes, missiles, ships at sea, and ground forces.

How did WWII bomb fuses work? ›

Fuzes have two purposes. The obvious one is to cause the bomb to explode. When the bomb makes impact, the fuze has a spike or electrical circuit that detonates the bomb. If the fuze has a spike, that spike is driven into a small detonation charge that sets off the main bomb charge.

How does an impact fuze work? ›

Impact, percussion or contact fuzes detonate when their forward motion rapidly decreases, typically on physically striking an object such as the target. The detonation may be instantaneous or deliberately delayed to occur a preset fraction of a second after penetration of the target.

What is the best gun to use with fuze? ›

After the light machine guns nerf that arrived with the launch of Operation Brutal Swarm, players quickly moved back to the AK-12 as the weapon of choice for Fuze, which is no surprise given that it's one of the strongest guns in the game.


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