Commanding officers had several “weapons” to hand which in theory could destroy a UBoat.

1.       The HEDGEHOG – was a system of several mortar bombs mechanically thrown into the sea in set patterns ahead of the ship, which had to touch the submarine physically for them to explode causing instant damage, and total destruction if all the mortars fired hit the target.

2.       The SQUID which took over from the hedgehog  -  was a system of 3 depth charges thrown from astern of the ship, over the full length to drop into the sea ahead of the ship. SQUID was fitted in my first ship a Castle-Class frigate.

3.       The LIMBO which took over from the squid – similar to the squid but more powerful and more accurate. LIMBO was fitted into one of my ships, a Type 12 frigate.

Weapons like the HEDGEHOG were much more potent if they hit than a depth charge,  which relied on doing shock-damage like popping rivets, bursting welded sections or collapsing paper-thin ballast tank metal plates .  A depth charge exploding very close to a submarine was a lethal if not more so than the mortars fired from a hedgehog.

The essence of a weapon fired over the length of the ship was that the ship was steering towards the known position of the submarine and therefore could more accurately place the depth charge on top of the submarine well before it arrived in the same position thereby protecting the hull of the ship, rather than as before, when the depth charge was fired from a launcher out to port or starboard from the waist aft, or rolled off the back of a ship running over the top of a submarine.

Depth charges used barometric [depth] fuses which could be set/adjusted even seconds before firing to take account of ASDIC/SONAR data. The fuse was very simple and worked on pressure which we are all familiar with. At normal times [on land not too far above  sea level heights and on the sea surface] the barometric pressure is approximately 15lbs per sq” just slightly under in reality at 14.7.  The higher we go the less the pressure until we reach a point where there is no pressure at all. Before an airliner takes off, the pilot seals the cabin [but not the hold] trapping the ground pressure so that we are comfortable throughout the flight. If that pressure fails and we are at high altitude, we need assistance to breath and hence the oxygen masks which automatically drop down from above our seat. At that point the pilot takes the aircraft down back towards earth until we no longer require the masks. Professional climbers of Everest, X2 etc use oxygen breathing system and that below a ceiling of 28,000 feet.   If however, we go under the sea, the pressure increases and as far as we know never stops increasing. At 100 ‘ it becomes 43.35 per sq “- at 500’ = 216.76 – at 1000’ = 433.51. HMS HOOD was found laying on the bottom of the North Atlantic off Iceland at a depth of 1.7 miles = 3901.63 per sq”.  Imagine having a dozen or so full grown African male elephants standing on your body all at the same time were that possible?

If we want to kill a submarine known to be at an  approximate depth of say 300’ [typical WW2 depth] then we need to set the pressure fuse to explode when the depth charge [still dropping remember to the sea bed] reaches 130 lbs per sq”. We would set others just above and another just below in case the submarine starts to take evasion action all the time pointing the ship at the known bearing of the submarine. Repeat firings could see those pressure setting adjusted accordingly at the twist of a knob.

For a submarine caught on the surface via WS [Warning Surface] radar at ranges up to 10,000 yards [5 nm] -  so the submarine, because of its height of eye to the horizon distance wasn’t aware of the ships presence – the ship could attack by radar controlled gunnery, accurate in range and azimuth [bearing] by guns or when closer by torpedoes. Weapons like the SHARK could be used. The SHARK [a missile which looked every bit a shell] was fired from a standard gun. It was specifically designed so that at short ranges and low trajectories it would not ricochet but continue its trajectory straight into the water. Thus, the missile was aimed to land just short of a surfaced submarine to strike the pressure hull, causing lethal damage. The system relied on highly accurate ranges. An outfit called RTC [Range to Contact] which gave a five yard step drum range receiver output  was fitted to the gun being used, making sure that accurate ranges were always readily available.  If the ship is fitted with SHARK and SQUID then the RTC served both cases for range accuracy.

These weapons and the introduction of WS radar were so successful, that they eventually destroyed the German UBoat  wolfpack attacks. Groups of UBoats, in mid Atlantic and as such out of the range of shore based Allied aircraft, would meet up in the vicinity of the tracks of east-bound convoys.  They would surface and at full speed on their main engines [diesels] infiltrate the convoys sinking ships with torpedoes and gunfire, often using weather conditions like mist or fog, at dawn or dusk and always catching the escort commanders by surprise. At the same time they would replenish the air quality inside the boat as well as charging their batteries.

This is what German Admiral Doenitz said in a speech at Weimar in late 1943, during the decline of the UBoat war from end ’43 onwards. He was specifically referring to his wolfpack tactics and our WS radar.

“The enemy has deprived the UBoat of its essential feature, the element of surprise, by means of radar. With these methods he has conquered the UBoat menace.  The scientists who have created radar have been called the saviours of their country. It was not superior strategy or tactics which gave success, but superiority in scientific research.”

The commanding officer had at all times the ability to use LA [low angle] conventional gunnery 4”/5.5”, bofor MKIV, very heavy machine guns or torpedoes to rout  a surfaced submarine, as well as the proverbial full speed ram to fracture the pressure hull and to sink the boat. Many ships in the fleet had some kind of strength and support forward of the cable locker/paint shop to effect a ram, and when not that, it was perfectly possible for a high speed approach square on the submarines beam to roll the boat over and force it under with her conning tower hatch low and open to the sea. It was even known in close proximity for heavy machine guns to be turned on the glass periscope lenses protector, in the hope of smashing them thereby revealing the delicate periscope lenses for subsequent destruction, making the vessel almost useless as submarine. As well as all these devices, the SQUID was an excellent tool against UBoats on the surface. Before firing, the pressure setting could be set 2.6 so that almost as soon as it hits the water at just 6’ down it explodes almost certainly  breeching the pressure hull.