The Forgotten Genius Behind Britain’s Secret Weapons

In the shadowy world of World War II’s clandestine warfare, two very different British operations unfolded simultaneously in 1943. At Baker Street, Margaret Jackson efficiently coordinated sabotage operations across Europe, delivering crisp nightly briefings to her superior. Meanwhile, in the Buckinghamshire countryside, a brilliant but reluctant weapons designer named Millis Jefferis worked in isolation, unaware of how his creations were changing the course of the war at sea.

This striking contrast between organized intelligence operations and ad-hoc weapons development characterized Britain’s wartime innovation machine. While Jackson received precise radio reports about nighttime sabotage missions, Stuart Macrae at the Firs estate struggled to get any feedback about the weapons they were producing at breakneck speed. The Firs had become an unlikely hub of invention, churning out “all sorts of marvelous weapons” – from bouncing bombs to bridge-destroying rockets – yet remained strangely disconnected from their operational use.

Birth of the Hedgehog: A Mathematician’s Weapon

Jefferis’s most sophisticated creation, the Hedgehog anti-submarine mortar, had begun development early in the war when both he and Macrae worked at the War Office. Originally conceived for sabotage operations during a potential Nazi invasion, it evolved into something far more complex. The weapon’s development highlights the challenges of wartime innovation – what began as a simple concept required two years of painstaking refinement.

The critical challenge lay in calculating the weapon’s recoil with absolute precision, essential for maintaining a ship’s stability. A newly recruited engineer witnessed Jefferis’s dedication firsthand during a train journey from Bath to London, where the mathematician “spent nearly the entire trip frantically calculating on empty cigarette boxes.” When the train pulled into Paddington Station, Jefferis finally smiled – his calculations had yielded results.

Sea trials proved the Hedgehog’s remarkable effectiveness. The projectiles, encased in streamlined shells, plunged into the water and struck their underwater targets with uncanny accuracy. Yet despite these successes, it wasn’t until spring 1943 that the first Hedgehogs were installed on Royal Navy ships, facing skepticism from traditional naval officers.

Naval Skepticism Meets Revolutionary Technology

The Royal Navy’s initial reaction to the Hedgehog typifies military resistance to unproven technologies. When Commander Reginald Whinney of HMS Wanderer first saw the weapon being unpacked at Devonport dockyard, he marveled at its bizarre appearance. “How does this thing work, sir?” he asked. “When do we use it?” The response – a shrug and promise of future instructions – did little to inspire confidence.

The Hedgehog’s 24 spigot mortars presented a radical departure from conventional depth charges. As one officer noted, many Royal Navy captains “were accustomed to weapons that made a lot of noise” and found little impressive about a contact-fused bomb that only exploded when hitting an invisible target. They preferred using tested depth charges, despite their dismal hit rate of less than one in ten attacks. Jefferis’s technology seemed too advanced to trust.

America Embraces the Future of Anti-Submarine Warfare

While British commanders hesitated, the U.S. Navy recognized the Hedgehog’s potential. By late 1943, American ships began installing the systems in large numbers. One such vessel, the USS England, would soon demonstrate the weapon’s devastating effectiveness in dramatic fashion.

In spring 1944, as Japan launched a campaign to destroy the American Atlantic fleet, Admiral Soemu Toyoda declared that “victory in the Philippine Sea depends on submarines.” Unbeknownst to him, his submarine fleet would soon face Jefferis’s ingeniously designed weapon in a series of lethal encounters.

The USS England’s Historic Hunt

On May 18, 1944, sonar operator Roger Bernhardt aboard the England shouted those electrifying words every anti-submarine crew longed to hear: “Strong, clear echo, sir!” Their target: the Japanese submarine I-16, commanded by the capable Takesuke Yoshitake. What followed would become a textbook demonstration of the Hedgehog’s lethal precision.

Lieutenant Commander John Williamson, the England’s executive officer, represented a new breed of naval officer – technically proficient and eager to embrace new technologies. As he tracked Yoshitake’s submarine, he marveled at the Japanese commander’s skillful evasive maneuvers. At 400 yards, the target executed a sharp turn and stopped its propellers, employing a “knuckle” maneuver to disrupt sonar tracking.

Williamson, however, remained focused. Using Doppler analysis, he calculated the submarine’s exact depth and at 2:33 PM, fired the Hedgehog. The projectiles arced through the air in perfect ellipses before plunging into the water exactly as Jefferis had designed. Then came the tense silence – unlike depth charges, Hedgehogs only exploded on contact.

The subsequent series of underwater explosions – four to six nearly simultaneous detonations – confirmed direct hits. Below the surface, the I-16’s hull crumpled like a tin can under multiple impacts. Yoshitake and his crew perished instantly in the catastrophic implosion.

A New Era in Anti-Submarine Warfare

The England’s crew erupted in celebration as evidence of their victory surfaced – cork insulation, prayer mats with Japanese writing, a single chopstick. Most chillingly, they observed sharks circling, drawn by unseen carnage below. This pattern would repeat itself with terrifying efficiency over the next twelve days as the England sank five more submarines using the Hedgehog, an unprecedented feat in naval history.

Some crew members expressed discomfort at how easily the Hedgehog destroyed enemy vessels. Williamson’s response captured the brutal calculus of war: “The more enemies we kill, the more ships we sink, the sooner this war will end.” This pragmatic outlook might have come directly from Jefferis himself.

The Strategic Impact: Silencing Japan’s Submarine Fleet

The consequences of these engagements reached far beyond individual battles. When Admiral Toyoda issued urgent orders on June 15 for Japan’s Seventh Submarine Fleet to intercept American ships near Saipan, he received a devastating reply from Rear Admiral Owada: “The Seventh Submarine Fleet has no submarines left.” Jefferis’s Hedgehog had destroyed them all.

This technological advantage proved decisive. As Macrae later noted with pride, “The Hedgehog was an outright winner… though it came into use late, it achieved the remarkable record of sinking 37 submarines.” What began as an anti-invasion weapon in Kent had been refined by Jefferis into one of the war’s most effective naval weapons.

Legacy of the Quiet Innovators

The Hedgehog’s story reveals important truths about wartime innovation. Jefferis, the reluctant weapons designer who preferred his mathematics and chalk to military glory, created a weapon that fundamentally changed anti-submarine warfare. His work, conducted far from battlefields and naval command centers, demonstrates how scientific brilliance could emerge from unlikely places.

Meanwhile, the contrast between Margaret Jackson’s efficient intelligence operation and the Firs’ isolated inventors highlights the diverse approaches Britain employed to fight the war. While coordinated sabotage operations received meticulous attention, revolutionary weapons development often proceeded with little oversight or feedback.

Today, the Hedgehog stands as a testament to the power of innovative thinking in warfare. Its success against U-boats paved the way for modern anti-submarine weapons, while its development story offers enduring lessons about overcoming institutional resistance to new technologies. Most importantly, it reminds us that some of history’s most significant military advancements often come from quiet thinkers working in obscurity, their cigarette-box calculations changing the course of conflicts far beyond their immediate view.