Why This ‘Absurd’ British Hedgehog Killed More U Boats Than Depth Charges Ever Did

November 1942, North Atlantic. A Royal Navy Corvette closes on a sonar contact. AIC pinging steadily against a submerged yubot 400 yd ahead. The captain gives the order. 24 bombs arc forward from the ship’s for deck. Hang briefly against the gray sky, then plunge into the sea 200 yd ahead. Silence. The crew waits.

Nothing. The Azdic operator calls out. Contact still holding. Bearing unchanged. Reload. 3 minutes later, another salvo. This time, three muffled thumps roll up through the hull. Oil and debris rise to the surface. The yubot is dead. No depth charge attack in the entire war worked like that. And that difference, that ability to keep hitting until something died, is why this absurd looking collection of metal spikes killed more submarines than depth charges ever could.

The numbers prove it. According to British Admiral T records, the hedgehog achieved a kill rate of 17 1.5% across 268 attacks. Depth charges managed 1.65% 65% across more than 5,000 attacks. That meant roughly 1 in6 hedgehog attacks resulted in a dead submarine. For depth charges, it was closer to 1 in 60. By late 1944, experienced hedgehog crews were achieving 35% kill rates.

One in three attacks ending in a confirmed kill. To understand why those numbers matter, you need to understand why depth charges failed so consistently. AIC. The British sonar system projected a cone-shaped sound beam roughly 10° below horizontal. As an escort ship closed on a submarine, the target slipped beneath this beam and vanished from detection.

Technical assessments show this blind zone created a dead time of 50 seconds or more between losing contact and depth charges reaching their target depth. The submarine disappeared from sonar at somewhere between 175 and 280 yd, depending on how deep it was running. German yubot commanders became experts at exploiting this window.

The standard evasion tactic was brutally simple. Wait for the attacking ship’s propeller noise to pass overhead, then execute a sharp 90° turn. A type 7 Cubote could complete this maneuver comfortably within the dead time. Chemical decoys called pillanwer released clouds of bubbles to create false echoes, drawing escorts away from the actual submarine position.

Bold decoys, as the British called them, were remarkably effective in the chaotic moments after a depth charge attack when sonar operators were struggling to regain contact. And even when depth charges did explode near a submarine, the underwater turbulence they produced blinded Azdic for up to 15 minutes. Thousands of tons of churning water scrambled the delicate sound waves that sonar relied upon.

The attacking ship essentially got one chance, then had to wait in frustrated blindness while its quarry fled into the Atlantic darkness. Convoys could not pause for extended hunts. Escorts had to rejoin their charges or risk leaving merchant ships unprotected against other hubots in the Wolfpack. U427 survived 678 depth charges in April 1945 alone.

The submarine was damaged certainly. Its crew was shaken and exhausted, but it survived precisely because depth charges could not reliably find and kill a deep running target. The weapon that had seemed so powerful, rolling barrels of explosive thunder off the stern, was fundamentally inadequate against a skilled commander with a room to maneuver.

The Hedgehog solved every one of these problems through three innovations that sound simple, but required genuine engineering brilliance to achieve. First, it threw bombs forward rather than dropping them a stern. The projectiles landed 200 yd ahead of the ship while Azdic contact was still solid. The blind time dropped from over 50 seconds to roughly 15.

Second, the bombs used contact fuses rather than pressure fuses. They detonated when they hit something hard at whatever depth that something happened to be. No more guessing how deep the submarine was lurking. Third, and this was the tactical master stroke, a mis produced no explosion. The bomb simply sank to the bottom without detonating.

The water remained undisturbed. Sonar kept working and the ship could reload and attack again within 3 minutes. With depth charges, a failed attack blinded sonar for a quarter of an hour. With Hedgehog, you could keep hammering until the target died or escaped beyond sonar range. The weapon emerged from the Department of Miscellaneous Weapons Development, a unit of fewer than 60 people that the regular Navy establishment dismissed as cranks and amateurs.

They worked out of offices at Portland Place in London, tested devices at an experimental station on Bernbeck Pier at Western Super Mayor, and collaborated with Churchill’s secret weapons workshop at a country estate called the Furs near Witurch. Among their number was Lieutenant Commander NS Norway, better known to the world as the novelist Neville Shoot.

The driving force was Commander Charles Goodiv, a Canadian-B born electrochemist who had joined the Royal Naval Volunteer Reserve as a midshipman in 1923. Good championed unconventional solutions with such tenacity that the phrase to do a goodieve, meaning to achieve something by hook or by crook, entered Royal Navy slang.

He faced constant opposition from established naval weapons departments who resented the intervention of what they saw as amateur scientists into their professional domain. The core technology came from Lieutenant Colonel Stuart Blacker, a territorial army officer who had developed the spigot mortar concept between the wars. His Blacker bombard used a metal rod that fitted inside the projectiles tubular tail with a propelling charge working against the spigot rather than requiring a conventional barrel.

Major Milis Jeffris at MD1, Churchill’s Secret Weapons Workshop, had productionized the bombard for army use. The naval adaptation was a partnership between Jeffris’s unit and Good Eve’s department. The decisive moment came in spring 1941. Good Eve arranged a demonstration for Churchill at Witurch. The prime minister initially refused to attend due to time constraints, but his daughter intervened.

We must see Captain Davis’s bombthrower, Daddy. Churchill watched the 24 round salvo fired two at a time, then demanded a second salvo, then a third. The next morning, first Sea Lord Admiral Pound sent for good even promised full support. Now, before we see how this performed in combat, if you’re enjoying this deep dive into British engineering, hit subscribe.

It takes a second, costs nothing, and helps the channel grow. All right, let’s get into the combat record. The Hedgehog fired 24 contactfused projectiles from four cradles of six spiggots each. Each bomb measured 7.2 in in diameter and approximately 46 in long, weighing about 65 pounds total with a 35B Torpex warhead.

Torpex was roughly 50% more powerful than TNT by weight. The bombs fired in ripple sequence, one pair every tenth of a second, highest trajectories first, so that all 24 landed simultaneously. The staggered firing eliminated the need for deck reinforcement, a critical advantage allowing easy retrofit to existing escorts.

The Mark 10 projector produced an elliptical pattern roughly 140x 120 ft. This pattern was experimentally optimized using a device resembling a roulette wheel with a scale model submarine over which tiny missiles were thrown for days. A type 7 CU boat measured 220 ft long by 20 ft wide. An accurately placed salvo virtually guaranteed at least one hit.

Reload time was approximately 3 minutes. The contact fuse was an engineering marvel. It had to survive the violent shock of water entry, but then detonate on the comparatively gentle contact with a submarine’s hull. The fuse armed only after entering the water and detonated exclusively on impact with a hard surface.

Admiral T trials confirmed that 30 lb of torpex detonated in contact with the submarine’s outer casing. Even 4 ft above the pressure hole would rupture it. At typical engagement depths, a single hole punched in the pressure hole flooded the boat at roughly 400 gall per minute. Compare this to depth charges. The standard British Mark 7 depth charge weighed 290 pounds with a 190 lb ammole charge.

It had to detonate within roughly 20 ft of a submarine’s hull to cause fatal damage, but the attacking ship had to guess the submarine’s depth and set the hydrostatic fuse accordingly. Early British charges were limited to a maximum setting of just 350 ft, while type 7 Ubot could dive past 700 ft. Even a near miss that shook the submarine violently but did not breach the hull allowed the target to escape while Azdic recovered from the blast turbulence.

The hedgehog eliminated every one of these variables. No depth setting required. No need to pass over the target. No sonar blackout after firing. And when it hit, it killed. No submarine is known to have survived a direct hedgehog hit. Despite its technical brilliance, the weapon initially stumbled.

It entered service in early 1942 and was fitted to over 100 ships by November of that year, yet produced no confirmed kills until November 1942. The problem was psychological. Depth charges always exploded, producing spectacular water columns that made crews feel they were accomplishing something, even on a total miss.

A hedgehog miss was, in one widely repeated phrase, discouragingly quiet. Commanders preferred the theatrical reassurance of detonations over the anticclimactic silence of a genuine miss. The Royal Navy used Hedgehog so rarely in early 1943 that a formal directive was issued ordering captains to explain in writing why they had not fired Hedgehog on underwater contacts.

An unprecedented bureaucratic measure reflecting deep institutional frustration. The turnaround came from training, not technology. The department dispatched an officer to HMS Ferret, the escort base at Londereerry, to conduct shipwide briefings with concrete examples of successful attacks. North Atlantic spray had been soaking launches and causing firing circuit failures.

Maintenance procedures were improved. The results were dramatic. In the first half of 1943, Hedgehog achieved a kill rate of 8 12% from 53 attacks. By the second half of 1944, that figure had risen to 35% from 37 attacks. The improvement came almost entirely from better training and tactics, not hardware changes.

By mid 1944, Hedgehog and its successor Squid together were sinking more Ubot than depth charges. The statistics tell the story with brutal clarity. Hedgehog accounted for only 4.9% of all surface ship anti-ubmarine attacks during the war. Yet, it delivered 32.3% of all surface ship submarine kills. The weapon was simply operating on a different level of lethality than anything that came before it.

The single most devastating demonstration of Hedgehog’s power came in the Pacific. USS England, a Buckleyclass destroyer escort, sank six Japanese submarines in just 12 days between the 19th and 31st of May 1944. The greatest anti-ubmarine achievement by any single warship in history. All six kills were made with Hedgehog. The victims belong to the Japanese 7th submarine squadron deployed as a picket line whose positions had been revealed by codereaking.

England’s attacks showed the weapon at its most efficient against RO116 on the 24th of May. She scored three to five detonations on her first salvo. Against RO1082 days later, four to six detonations on the first attack, the final kill, RO105, was the most dramatic. After other ships in the Hunter Killer Group fired over 20 failed attacks across 25 hours, England was called in and sank it with a single salvo.

Her escort division commander signaled, “How do you do it?” Admiral Ernest King declared, “There will always be an England in the United States Navy.” In the Atlantic, USS Eugene Elmore’s engagement with U549 on the 29th of May. 1944 perfectly illustrated Hedgehog’s tactical advantage. After U549 torpedoed and sank escort carrier USS Block Island, Elmore tracked the Yubot at extreme depth below the 600 ft depth charge limit, her first hedgehog salvo missed.

But because the miss was silent, sonar contact remained unbroken. She reloaded, fired again, and scored three hits. Four minutes later, the sound of U549 imploding was recorded. A depth charge attack in the same circumstances would have blinded sonar for 15 minutes while the submarine escaped into the deep. Dunit’s withdrawal of yubot from the North Atlantic on the 24th of May 1943 known as Black May reflected the cumulative impact of radar air power codereing and improved anti-ubmarine weapons including hedgehog. In that single month Germany

lost 41 yubot against 50 Allied ships sunk. The exchange rate had become catastrophic. For the first time in the war more were dying than merchant vessels. German tactical adaptations came desperately. Snorkels from mid 1944 allowed submarines to run diesel engines while submerged, but reduced speed and maneuverability.

The revolutionary type 21 electroboot promised underwater speeds of 17 knots, enough to outrun most escorts, but only two entered service before the war ended. Germany never developed equivalent forward throwing weapons, being predominantly the submarine operator rather than hunter. The Creeks Marine understood that something fundamental had changed in anti-ubmarine warfare, but could not reverse the technological tide.

The Hedgehog established a principle that reshaped all subsequent anti-ubmarine warfare. Attack while maintaining sonar contact, not after losing it. Every modern anti-ubmarine weapon system descends conceptually from this insight. The immediate successor was Squid, a three-barreled 12-in mortar ordered from the drawing board in 1942 and rushed into service by May 1943.

Squid fired three 390lb depthfused bombs using a clockwork time fuse automatically set by the ship’s sonar range recorder, eliminating human depth guessing. The bombs were far larger than hedgehog projectiles, each carrying 200 lb of minol explosive compared to 35 lb of torpex. Double squid installations achieved a 2.

45 to1 attack to kill ratio, the war’s best. Where hedgehog required a direct hit, Squid could kill with a near miss through sheer explosive force. Limbo followed in 1955, adding gyro stabilization, automatic loading, and variable range from 400 to 1,000 yd. The three barrel mortar could be trained and elevated automatically with a mechanical computer calculating firing solutions from sonar data.

Limbo saw combat as late as the 1982 Falklands War and served into the 1990s aboard Royal Navy Frigots. The Soviet Union recognized the Hedgehog’s value immediately. They produced the MBU200 in 1949, a direct copy, evolving into the RBU 6000 Smurch 2, a 12 tube rocket launcher, explicitly described as similar in principle to the Royal Navy Hedgehog System.

The RBU 6000 remains in Russian service today and has been repurposed as a land attack weapon in Ukraine, mounted on truck chassis and tank holes to deliver salvos of unguided rockets against ground targets. a peculiar modern echo of a weapon designed to kill submarines 80 years ago. The Americans retained Hedgehog into the Cold War before replacing it with Weapon Alpha and ultimately Azrock, which extended the forward throwing concept to multi-mile ranges using rocket delivered torpedoes.

The principle remained identical. Attack from a distance, maintain sonar contact, keep hitting until the target dies. Every NATO frigot and destroyer today carries weapons that trace their tactical lineage directly to that collection of spiggots bolted to Corvette Ford decks in 1942. The Hedgehog’s story contains a powerful irony at its heart.

The weapon that saved the Battle of the Atlantic was initially rejected because it did not make enough noise. Sailors wanted the satisfying thunder of depth charges. Weapons that killed at a rate of 1.65%. The Silent Hedgehog with its unnerving lack of feedback on a miss killed at 10 times that rate. Human psychology demanded spectacle.

Engineering demanded results. It took two years of institutional struggle before results won. The transformation required not just engineering innovation from outsiders like Good Blacker and Jeffris, but a psychological shift in how the Royal Navy understood combat effectiveness. They had to learn to measure results by submarines sunk rather than explosions witnessed.

That shift, forced through by a unit of 60 misfits against institutional resistance, turned a weapon that looked absurd, a hedgehog of metal spikes bolted to a ship’s deck, into one of the most decisive innovations of the Second World War. The depth charge had its chance. Thousands of attacks, countless explosions, spectacular water spouts rising against Atlantic skies, and a kill rate of less than 2%.

The Hedgehog asked for nothing but silence and patience, and it delivered a kill rate 10 times higher. 11 of the last 16 Yubot kills by American destroyers and destroyer escorts came from hedgehog attacks. By the war’s end, forward throwing weapons had proven themselves so comprehensively that depth charges became secondary arament kept aboard for area saturation rather than precision killing.

British engineering was not always elegant. Sometimes it looked ridiculous. Sometimes it took outsiders to make the establishment listen. But when it mattered, when the Battle of the Atlantic hung in the balance and Ubot was strangling Britain’s lifelines, a Canadian electrochemist and a collection of eccentric inventors created a weapon that transformed submarine warfare forever. The Hedgehog worked.

The numbers proved it beyond any doubt. the

Note: Some content was generated using AI tools (ChatGPT) and edited by the author for creativity and suitability for historical illustration purposes.