Someone as little friend of pessimism as Winston Churchill claimed that, during World War II, he had only feared one thing: the submarines flying the swastika flag. He was very right. During the contest, the metropolis barely produced 15% of the food that its citizens needed to survive; the rest, on the contrary, had to reach across the sea. Therefore, when the British Prime Minister realized that Adolf Hitler sought to block maritime traffic across the Atlantic and destroy the freighters that nurtured his beloved Britain, he shuddered in his armchair.
The same happened in the United States, a power that saw Britain as a giant supply store since launching an attack on old Europe. If they couldn’t safely transport material across the ocean, they would have trouble beating the Nazi giants. Therefore, both giants began an arms race that sought to end the threat that, during the entire Second World War, posed the German U-Boote. For this they devised from the popular depth charges, to a curious weapon dubbed “hedgehog” that brought together a great destructive power. On one side we leave the aircraft carriers, of which we have already spoken extensively throughout these years.
1-Depth and Torpex loads
During the war against Adolf Hitler and his swastika, one of the most economical ways that allied ships that sailed on the surface had to try to send a submerged German U-Boot to the bottom of the ocean was using depth charges. These weapons, invented during the First World War, were formed by a metal cylinder in which an amount of explosive was introduced that could range between 150 and 300 kilograms (approximately the same amount as the torpedo of a submersible).
Once loaded, it was thrown from a ship or a plane to the bottom of the sea with the sole objective of destroying any enemy submarine that was in the area.
Its operation was simple. To begin with, allied ships or airplanes had to detect the area of the sea in which the U-Boot was located, crouched under water. Next, they were placed on top of it, regulating the detonator of the charge to a certain depth and finally throwing it. «In essence, the depth charge was formed by a drum [lleno de explosivo] and a fuze based on a pressure gauge that was activated when it reached a certain depth ”explains Carlos Martí Sempere in his book« Defense technology: analysis of the Spanish situation ».
Once submerged to the marked depth, the charge exploded causing a large shock wave that could cause serious damage to the submarines that were nearby. However, their goal was not only to sink those eggshells, but to cause them so many damages to force them to rise to the surface. And, once they were under the blue sky, they could be shot occasionally and even forced their crew out on legs (or swim, rather) with a surface cannon.
“Although its lethality radius was about 5 meters, which made the probability of destruction very low, the combined action of multiple loads could cause enough damage to the submarine’s hull or its equipment to force it to return to the surface, because the shock waves they created under the water reached further, thanks to the excellent transmission of water energy, ”adds Sempere in his work-
In turn, and contrary to what the factory “Hollywood” has transmitted to us with its epic films, it was not necessary for deep charges to touch the enemy ship to fulfill its function. «To cause damage, contact with the submarine was not necessary. In a radius of ten meters it could cause serious damage, and the cumulative effect of several charges could send a submarine to the bottom »Juan Vázquez García points out in his work« U-Boote. The legend of the gray wolves ».
Although its blind launch made it not easy to hit a U-Boot, depth charges could be lethal if they hit the target. In fact, they not only caused the submarine’s hull to break or damaged its vital components, but also had severe psychological effects on the crew, which had a hard time enduring the terror of knowing that they could die in the most remote seabed .
Despite its low cost compared to that of other anti-submarine weapons, depth charges also had several drawbacks. Among them, that the explosions they generated were of such magnitude that they used to leave the SONAR of the ship unusable for several minutes (since the instrument was covered by the sound and turbulence generated by the explosive). This prevented locating any submerged enemy, exposing the warship to a possible attack. In addition, he allowed the U-Boot to escape without being discovered if his captain had enough skill to dodge the explosives.
In principle, depth charges were loaded with TNT, then Torpex was used
It was also necessary to know the depth to which the U-Boote was submerged – something very difficult – to be able to program the explosion of the depth charges. A new added difficulty was that these weapons should always be launched from the stern or the sides of the ship, which caused SONAR to lose sight of the target. Specifically, this situation occurred because, when the operation of the sound waves under water was still unknown, they used to create “zones of silence” (places where submersible enemies could not be detected by instruments) behind the ship.
Finally, the captain of the ship launching the deep charges could not be sure that the explosives had reached the enemy submarine. “Another problem was that there was no way of knowing the damage caused, and since a charge took 25 to 75 seconds to explode, depending on the depth the U-Boot had, in theory, the possibility of escaping,” adds the Spanish author in your text
In principle, and until well into World War II, depth charges used to go to the top of TNT (trinitrotoluene). This explosive, first manufactured in the nineteenth century, stood out for being very stable (that is, for preserving its properties for a long period of time and for not exploding without warning – something that, no doubt, was appreciated on ships that sailed the seas in 1939-). In turn, it was one of the cheapest components with which to manufacture brutal bombs at that time.
The effectiveness of this explosive caused it to be one of the most used during the conflict. «Trinitrotoluene is a yellow, odorless solid that does not occur naturally in the environment. It is commonly known as TNT and is an explosive used in military projectiles, bombs and grenades, in industry, and in underwater explosions, ”explains the“ A gency for toxic substances and disease registry ”(“ Agency for Toxic Substances and the Registry of Diseases ») in its dossier« 2,4,6-Trinitrotoluene ».
However, at the end of the contest the depth charges ended up filling Torpex, an explosive twice as powerful as the Trinitrotoluene and which, thanks to its ability to prolong the explosions, quickly gained a place among the war contenders . «Torpex had its shortcomings. He was more sensitive to accidental detonation than the TNT and was more fragile, but he gave the additional power needed to fight, ”notes Robert Gennon in his book“ Hellions of the Deep: The Development of American Torpedoes in World War II ”( which analyzes the development of the explosives used during World War II).
After years using depth charges, and once these weapons were outdated, the Allies began the search for an artifact capable of ending more effectively with the Nazi “Wolf Pack” (which had long been playing what untouchable ships that tried to send food and ammunition by sea to the British). At the same time, it was established that it was no longer only worth detecting them or attempting – through explosives – to bring them to the surface, but that it was intended to give them a ticket without return to the bottom of the sea abyss in a single and accurate blow.
The solution came from Charles Goodeve. Naval scientist by profession, this young Canadian devised in 1943 – year in which Nazi submarines dominated the waters of the Atlantic based on torpedo and cannon – a novel anti-submarine system that was known as the “Hedgehog.” This weapon consisted of a small rocket launcher that, from the bow of any warship in which it was installed, fired several grenades against the sea at one time within a certain range of action. A revolution for a time when the main method of sinking a submarine was the ancient and random depth charges.
The genius who invented the “Hedgehog” came into the world on February 21, 1904 in Manitoba (in the middle of Canada). Of humble origin, Goodeve discovered his interest in science in the institute and soon stepped on the university where, in 1925, he graduated with honors in physics and chemistry. At that time, and although he felt a great love for navigation, it was impossible for him to think that – several years later – he would end up building weapons systems to fight against Nazism.
Goodeve created a revolutionary weapon with multiple advantages over depth charges
“During his third year at the University, Charles’s interest in the naval world led him to join Canada’s voluntary naval reserve, where he became a midshipman. […]. Although he wanted to be an officer, he soon discovered that his future was in England, where he traveled with a scholarship. […]. There, Charles continued with his naval and military interests serving four battleships and three destroyers. He graduated as a torpedo specialist and, later, also specialized in the electrical part. In 1936 he was promoted and began to direct his research towards naval problems, ”explains the Naval Museum of Manitoba in an untrusted dossier called“ Sir Charles Goodeve ”.
After the start of World War II, and after observing how fearsome a single U-Boot managed by an experienced Nazi captain could be in the Atlantic, Goodeve began to break his head by finding a weapon that would protect allied ships. And, at that time, German had established a blockade with its submersibles over Britain to prevent any ally ship from bringing food, ammunition or weapons to the islands. Thus, dozens of convoys had been sunk by the submarines of the Führer.
A strange weapon is born
Shortly after, in 1941, Goodeve had already developed the prototype of a revolutionary weapon that, after several tests in Liverpool Bay, was acquired by the “Royal Navy” under the name of MK 10 anti-submarine mortar shuttle. “The device was developed by the British. [Estaba formado por una plataforma de disparo] which launched 24 tang mortars at a maximum distance of 250 meters. He settled on the bow of the attacking ship and fired a savior that fell on the sea describing a circle with the aim of hitting any submerged enemy, ”explains the American“ Destroyer Scort Historical Musuem ”in his dossier“ Hedgehog ”(“ Hedgehog ” ).
The MK 10 grenades were first shot towards the sky and then dropped into the water and sank into it. In turn, they were launched in such a way that, when they reached the sea, they did so covering a large area of several meters in an elliptical or circular shape. In this way, it was intended that the U-Boote captains had a hard time escaping. Once under the ocean, its operation was simple: if they played even if it was the periscope of an enemy submarine, it could be considered dead.
“Each of the 24 bombs measured 20 centimeters and contained an explosive charge of about 30 pounds [14 kilos] TNT or 35 pounds [16 kilos] from Torpex. They were not rockets, as they had to be propelled by a shuttle. These “grenades” were activated and exploded by contact, that is, they only detonated when they hit a submerged enemy, such as a submarine. One or two of them could sink the submersible, ”adds the“ Destroyer Scort Historical Musuem ”. On the other hand, it was not long until, due to the shape of the grenades in the device before being fired, this anti-submarine system began to be known as “Hedgehog” (well, when the explosives were placed on the shuttle, they resembled the barbs of this animal).
In principle, the “Hedgehog” was designed to retire once and for all the old depth charges. And, among other things, these outdated weapons should always be fired from the stern (which prevented attacking a submarine located in front of the warship); they were extremely inaccurate (the distance to which they should explode should be regulated by hand and, in principle, at the discretion of the captain); and, finally, its explosion prevented SONAR from locating any enemy for several minutes. However, throughout the war the two weapons were used in combination with a single objective: to win the battle located in the Atlantic against the U-Boote.
In addition, and as the North American agency explains in its article, the fact that the device could be fired from the bow of the warships was a great revolution in the fight against the submersibles of the Führer: «The” Hedgehog “was developed by the British to overcome the main deficiencies of the attack with depth charges, and the main one was associated with SONAR. During World War II, SONAR could only scan [localizar] to the objectives that will be in front of the ship. Therefore, depth charges, when launched by stern, were shot blindly and without certainty of the enemy’s position. Located near the bow, the “Hedgehog” had the advantage of firing in front of the ship, which allowed it to maintain contact with the submersible ».
The “Hedgehog” was also much more destructive than depth charges. And, while these old explosives used the shock waves caused after the detonations to sink the submarines (in a few cases) or force them to rise to the surface (something more usual), the grenades of the new device burst directly on the submersible. This caused damage that, in the worst case, could end the maritime adventure of the U-Boote crew or, at a smaller level, caused severe damage to the submarine. In addition, hearing how dozens of small bombs hit the ship’s hull should not be very reassuring for Nazi sailors.
In addition to weapons, explosives and location systems, the allies also built all kinds of ships with which to send Hitler’s U-Boote to the bottom of the ocean. Among the most notable of the time were the “Flower” class corvettes, ships created during the first years of the Second World War to fight against the cunning war that German submarines carried out under water and, day after day, were He claimed the lives of hundreds of sailors. Cheap and simple to manufacture because their design was based on that of a civil ship, these ships served as an escort for a good part of the contest to merchants who crossed the Atlantic loaded with provisions to Britain.
To understand the causes that motivated the creation of the “Flower” it is necessary to go back in time until before the Second World War. It was in January 1939 when the British Admiralty (the mandamases of that time) considered designing a type of warship of reduced cost, easy to build and, above all, that had the ability to stop submarines from neighboring Germany In case of war. The government’s concern was justified because, almost 20 years earlier, the U-Bootes had proven to be a weapon to consider in the First World War and had not yet found an efficient way to destroy them without investing a good amount of pounds.
The one chosen to carry out this task was a company – located in the north of Great Britain – that had already worked designing ships for the Royal Navy in past conflicts. “The English Admiralty had to resort to the same firm used in the Great War, Smith’s Dock Company, of Middlesbrough. This shipyard’s solution was a design by engineer William Reed that adapted to the need for emergency manufacturing, ”explains naval historian Carlos López Urrutia in his dossier“ Canadian Corvettes in the North Atlantic ”.
The whaler that was corvette
To follow the requirements established by the government, Reed designed a military ship based on the basic characteristics of the Southern Pride whaler. Civil in nature, this ship had begun to be assembled in 1936 and its construction did not keep secrets for naval industry workers. Its simplicity, moreover, would allow it to be mass-produced by both military and commercial shipping companies, which would also reduce the cost of production. All in all, the Smith’s Dock Company had to make some changes to the original sketch. “The” Southern Pride “was a very sailor ship, but it had to be equipped with more powerful machines to give it greater speed”, the expert completes in his text.
The design, as expected, was quickly accepted by the “Royal Navy”, which soon ordered the first units from the shipyard in an attempt to quickly create an anti-submarine fleet capable of facing neighboring Germany. Due to its small size, the admiralty integrated this new vessel into the category of “corvette”, a term that defines a small, maneuverable and fast vessel, although poorly protected against enemy attacks. However, and due to its small size, it was established that, in principle, the ships that were delivered would be destined for missions near the coast.
The “Flower” – as they were finally known because the British baptized them with flower names – became, by their characteristics, the perfect anti-submarine ships. And, although they were quite slow – they reached an average speed of 14 knots compared to 18 of a surface submarine – they had an advantage over the military ships of the time. «Its turning radius was smaller than that of a submarine. He could turn in a radius of 400 yards. This is how this ship built to cover an emergency was so versatile and practical, ”says Urrutia.
The war begins
Everything would change radically with the beginning on September 1, 1939. And, after the Nazi troops put their boots on Poland, Hitler sent his U-Boot into British waters with the aim of establishing a naval blockade on the islands . The Führer also ordered his captains to fire on all that merchant ship with the intention of entering or leaving an English port. In this way, he intended to prevent the great allied convoys from bringing the food necessary for their survival to the islands. The objective, therefore, was to starve the enemy until he had no choice but to surrender.
«[Los alemanes llevaron] the war to the Atlantic and tried to juggle there a traffic without which Britain would soon be reduced to impotence, not only for lack of liquid fuel to move its merchants and its airplanes, because not a single liter of fuel was extracted in the British Isles, but out of hunger, because England did not produce at that time nor 20% of what its population needed to consume ”, highlights the Spanish historian Luis de Sierra in his work« The naval war in the Atlantic ».
Months later, Britain was clear that if he wanted to survive the war, he should escort his convoys so that they could resist the attacks of enemy submarines. However, their wishes were limited by the lack of cash and time to build transatlantic vessels. The need to defend their merchants, on the other hand, made them sharpen their ingenuity and caused them to make the decision that the “Flower” type corvettes were in charge of escorting ships arriving from the United States.
«The English high command had recognized the great danger they would have to face in the Atlantic […]. They were going to need escort ships, hundreds of them, and there simply weren’t. The Admirals were convinced that the destroyers, traditional escort ships, were too complex to build in any shipyard. [Por ello, se seleccionó a las “Flower”] assigning them the task of protecting merchant convoys until better ships could be built, ”López Urrutia explains in“ Canadian Corvettes in the North Atlantic. ”
In addition to their great mobility, the “Flower” were loaded to the brim with all kinds of elements with which to catch the herds of “Gray Wolves” Hitler (name that received the small fleets of U-Boote lurking under the waters). In the anti-submarine fight, the main weapons of these corvettes were deep charges, which could be launched from both sides of the ship. Over the years, they were also equipped with the “hedgehogs.” Finally, these patrols also had the ASDIC detection team (later called SONAR).
As far as surface combat is concerned, the “Flower” had a wide variety of weapons to defend themselves. The main one was a 4-inch cannon (a caliber not too large for a ship of these dimensions), a “pom-pom” (a 1.5-inch automatic cannon characterized by its rapidity when firing) and, to to finish, several anti-aircraft machine guns with which to demolish the enemies that, from the sky, will try to cause the occasional headache. Unfortunately, these corvettes had no defense against torpedoes, so if an enemy U-Boot managed to escape their attacks, they could easily end them.
During the war, these corvettes proved effective on multiple occasions. This is evidenced by the more than 60 casualties that managed to make Hitler’s U-Boote and the large number of them that were used. «Many” Flower “were dumped in the first months of World War II at shipyards in the United Kingdom and Canada, and were soon used in all areas, including mining. A total of 269 were built and served in the “Royal Navy”, the US Navy, the French Navy, the Norwegian and the Canadian Navy. They also served on the other side: four were captured by the Nazis, ”says Doug Thomas in“ The last flower. ” .