Nazi Submariners Were Right to Fear the World War II Hedgehog Mortar

March 24, 2025

The mechanical Hedgehog proved itself to be a deadly predator and killer of Axis submarines.

When one thinks of antisubmarine warfare (ASW) weapons of World War II, chances are the depth charge is the first weapon that comes to mind. This is understandable, since it was certainly the predominant ASW weapon type of that war (as well as World War I; Britain’s Royal Navy developed the depth charge back in 1916).

Depth charges could be indeed quite devastating, not just in terms of physical but also psychological effects upon enemy submarine crews, as dramatized in classic war films such as The Enemy Below (1957) starring Robert Mitchum and Curd Jurgens and Das Boot (1981) starring Jürgen Prochnow. The former film has remarkably good special effects for a film of its time, whilst the latter movie’s depth charge attack scene is a cinematic tour-de-force of sheer intensity.

The problem with depth charges was that they weren’t terribly efficient or accurate, as they were basically the underwater equivalent of “dumb bombs.” Hence, the Royal Navy developed a deadly efficient ASW weapon to complement its depth charges: the Hedgehog spigot mortar.

Hedgehog Initial History and Specifications

As noted by the Dark Skies MSN channel in the text caption to their video titled “The Super Weapon that Turned German U-Boats into Scrap“:

“In a top-secret effort led by the British Admiralty, a revolutionary anti-submarine weapon was developed—one that would forever change naval warfare in World War II. Instead of relying on traditional depth charges, which caused damage through hydrostatic shockwaves, engineers devised a weapon that would launch explosives ahead of a ship, detonating only on impact with a submarine. The initial Fairlie Mortar failed, but from its shortcomings emerged the Hedgehog, a devastating new tool in the fight against Nazi U-boats and enemy submarines in the Pacific. With its deadly precision and relentless effectiveness, the Hedgehog became one of the most feared anti-submarine weapons of the war.”

Designed in 1941 by the British Admiralty’s Directorate of Miscellaneous Weapons Development (DMWD)—nicknamed the “Wheezers and Dodgers“—the Hedgehog was also adopted by the U.S. Navy and Coast Guard in 1942 as a sort of reverse Lend-Lease favor.

Tech specs of the Hedgehog, courtesy of Mark Lardas of Military History Now, were as follows:

Length: 46.5 inches
Diameter: 7.2 inches
Weight: 65 lbs. overall; 35-lb. Torpex warhead

The weapons system consisted of twenty-four projectiles mounted six deep and four across on a steerable launcher, fired from their launch tube by a small propellant charge. The complete assembly gave off the appearance of a bristling hedgehog, hence the nickname.

Operational History and Performance

Sonic the Hedgehog jokes notwithstanding, the flesh and blood namesake of the Hedgehog rocket, i.e., the spiny mammal of the subfamily Erinaceidae, in the Eulipotyphla order, may look rather cute and cuddly from a distance (until you get up close and personal with its spines). However, it is in fact a predatory animal and therefore a killer, devouring insects, snails, frogs and toads, snakes, bird eggs, and carrion. Likewise, the mechanical Hedgehog proved itself to be a deadly predator and killer of Axis submarines.

As noted by the NavWeps website, “In the first few months of the war only 5 percent of all depth charge attacks were successful. Normal combat conditions reduced that figure to 3 percent. Combat records showed that in early 1942 the lethal probability of a single depth charge pattern (barrage) was about 3 percent and five attacks would raise the chance of a kill to about 10 percent.” By contrast, “In mid-1944, the USN was claiming an 8 percent kill rate with a single Hedgehog pattern. By the middle of 1945, that figure had risen to 10 percent.”

The most successful Hedgehog-wielding hunter of the war was also the single-most successful killer of Axis submarines amongst Allied warships, period, that being the Buckley-class destroyer escort USS England (DE-635), which sank six Imperial Japanese Navy (IJN) submarines.

Besides the greater accuracy, the Hedgehog had several other advantages over depth charges:

Faster sink rate (half the time of the older depth charges and 50 percent faster than the Mk.9)
No sonar “blind spot”; this was due to the fact that the Hedgehog was fired ahead of the ship, so sonar contact could be maintained with the target sub throughout the attack. By contrast, surface warships using depth charges had to pass directly over the target, thus creating the blind spot.
Somewhat along those lines, if a depth charge explosion failed to destroy or at least significantly damage the enemy sub, that sub could make an escape whilst the attacking surface vessel’s sonar was temporarily “deafened” by the blast; by contrast, since a Hedgehog projectile exploded only if it made contact, the sonar operator didn’t have to worry about being deafened if the projectiles missed.
No depth limit; by contrast, depth charges had a limit of 600 feet.

Where Are They Now?

The Royal Navy replaced the Hedgehog with the Squid and Limbo ASW mortars, whilst the U.S. Navy retained the Hedgehog well into the Cold War, when they replaced it with the RUR-5 ASROC (“Anti-Submarine Rocket”).

As far as I can ascertain, at least two Hedgehogs have been preserved for posterity in museums: one at the National Museum of the U.S. Navy in Washington DC, and the other at the USS Silversides Submarine Museum in Muskegon, Michigan. (If any of you dear readers out there know of any other Hedgehog museum displays, please let us know. Thanks in advance!)

About the Author: Christian D. Orr

Christian D. Orr was previously a Senior Defense Editor for National Security Journal (NSJ) and 19FortyFive. He is a former Air Force Security Forces officer, Federal law enforcement officer, and private military contractor (with assignments worked in Iraq, the United Arab Emirates, Kosovo, Japan, Germany, and the Pentagon). Chris holds a B.A. in International Relations from the University of Southern California (USC) and an M.A. in Intelligence Studies (concentration in Terrorism Studies) from American Military University (AMU). He has also been published in The Daily Torch, The Journal of Intelligence and Cyber Security, and Simple Flying. Last but not least, he is a Companion of the Order of the Naval Order of the United States (NOUS). If you’d like to pick his brain further, you can ofttimes find him at the Old Virginia Tobacco Company (OVTC) lounge in Manassas, Virginia, partaking of fine stogies and good quality human camaraderie.

Image: Wikimedia Commons.