Ultra D-Type Submarines (Japan)
Since the end of 1941, the Japanese Imperial Fleet regularly tried to use several types of ultra-small submarines in battles. The results of the combat work of such equipment could not be called successful: until the end of the war, submariners were able to sink or damage only a few enemy ships. At the same time, several dozen submarines were lost, and almost all of their crews died. However, the command fleet did not lose hope. At the beginning of 1944, another attempt was made to create a very small boat capable of covertly attacking the enemy. The new project received the designations type "D", "Tei-Gata" and "Koryu".
General ideas
By the beginning of 1944, the situation in the Pacific theater of war of the Second World War had seriously changed. The Japanese command still could plan sabotage in the ports and on the bases of the enemy, but the situation forced him to begin preparations for the defense of his own coast. While maintaining the current trends in the foreseeable future, the issue of protecting the coast of Japan from American ships and landing forces became topical. It is the need to protect the coast and coastal waters was the main reason for the emergence of the project "D".
Unfinished submarine type "D" in one of the factories. Photo Ibiblio.org
In developing the Tay-Gata project, Japanese engineers decided to abandon the approach used earlier. Ultra-small submarines of types "A", "B" and "C" were a consistent development of the same design, carried out using different components and assemblies. Despite numerous improvements, the newer boats retained the old hull, which did not always have a positive effect on performance. In the new project “D” it was proposed to use some existing ideas, but to develop the submarine again.
The refusal of the old building was associated with some new requirements and with the inability to enter the necessary units in the existing volume. Increasing the size of the boat within reasonable limits, in turn, allowed the use of new components with the required characteristics. Thus, the increase in size and weight was accompanied by an increase in a number of important parameters. Thus, it was possible to increase the volume of fuel tanks and thereby provide a new increase in the cruising range.
Design
The submarine of type “D” had a total length of more than 26 m, the maximum diameter of the robust hull exceeded 2 m, the height of the structure (with a wheelhouse) reached 3 m. The increase in size compared to previous submarines led to an increase in displacement to 60 t in a submerged position. It was expected that a larger and heavier submarine with the help of new powertrain units would be able to retain the required characteristics.
The scheme of the submarine type "D". Figure Ibiblio.org
According to the results of testing and operation of ultra-small submarines of the previous types, it was decided to seriously rework the hull structure. To improve the basic characteristics, both the design itself and the layout of the robust case were changed. Now it began at a short distance from the bow, and a propeller and steering gear was located at its stern. The bow of the strong body had the shape of a truncated cone, the middle - the cylinder. Several tail compartments were also made in the form of cones of different heights and diameters. In the middle part of the hull was cutting. To improve seaworthiness, a narrow and long superstructure was fixed on the upper surface of a solid hull, forming a characteristic vertical nose.
Large openings for the installation of torpedo tubes were provided in the nasal wall of the strong hull. Two such devices were placed one above the other, their backs were located inside a robust case. To simplify the maintenance of equipment, the crew had access to the nose torpedo compartment and could from there control the work of weapons. Behind the compartment with torpedo tubes there was another habitable volume, under the floor of which were batteries. Under the wheelhouse, a relatively large central post was provided. The crew of the submarine of the type “Koryu” was to consist of five people, because of which it was necessary to significantly change the layout and size of the inhabited compartments.
Directly behind the central post was a diesel engine with a generator. Behind this compartment, a free volume was provided with part of the batteries. The running motor connected to the propeller shaft was located in the aft compartment. The “D” type boat had one propeller placed on the hull aft hull. On the case in front of the screw there were rudders and depth rudders.
View of the torpedo tubes. Photo Ww2db.com
Compartments durable hull divided by several bulkheads. To move from compartment to compartment, the crew had to use openings-hatches. Manhole covers, in order to save space, were not provided. Thus, the flooding of one of the compartments could lead to the ingress of water into the neighboring ones.
Inside the lightweight superstructure, as well as inside the robust hull, there were several ballast tanks, which allowed diving to the desired depth and balancing. Compressed air cylinders for the purging of tanks were distributed over the free volumes of the hull. For example, two such tanks were located next to the torpedo tubes.
Increasing the size of the hull allowed the use of a diesel engine with an output of 150 hp. The consequence of this was a reduction in the time required to fully charge existing batteries. Now this process took no more than 7-8 hours. The electric motor with power 500 hp was responsible for the movement. Apparently, the calculations showed that the preservation of the old 600-strong engine will not give any particular advantages, although it will affect the size and weight of the whole structure.
When moving on the surface, the submarine of the type “D” could reach a speed of no more than 10-12 nodes. Maximum speed under water did not exceed 16-18 nodes. Thus, at maximum speed, the new submarines were noticeably inferior to their predecessors. However, Japanese engineers managed to significantly increase the cruising range. When using a diesel engine and a speed of no more than 8 units on one refueling, you could go up to 1000 nautical miles. On 16 nodes under water, batteries provided a range of 125 miles. The strength of the hull was enough to dive to a depth of 100 m.
The armament of the new submarine was borrowed from the old ones. In the bow of the submarine were two torpedo tubes caliber 450 mm. The main armament of the boats "Koryu" were torpedoes "Type 97". Such weapon could reach speeds up to 45 nodes and deliver a combat unit with a weight of 5,5 kg to a range of 350 km. The torpedo tubes of the ultra-small submarine were made muzzle loading. Because of this, submarine ammunition consisted of only two torpedoes. To recharge before attacking new targets should return to the base.
Interior of the central post. Photo Ww2db.com
According to reports, the crew of the submarine "Tay-Gata" consisted of five people. A co-driver and a torpedo were added to the commander, helmsman, and motorist. The increase in crew led to the need for improvements in habitable volumes, but allowed to reduce the load on an individual submariner. It was assumed that five people will be able to work without any difficulty for several days, occasionally replacing each other. Estimated travel range in combination with the maximum estimated patrol time forced the designers to pay special attention to the physical capabilities of the crews.
The central post of the type “D” submarine was equipped with all the necessary equipment. Submariners were able to monitor the situation above the water and underwater with the help of a periscope and hydrophones. A compass and a number of other equipment were used for navigation. On several dashboards there was a set of various analog instruments and other types of indicators. The crew could monitor the operation of all systems, both instrumentally and visually. For example, the mechanic had access to both engines and could perform all operations for their maintenance.
Mass production
Despite the need for a lot of complex design work, the project “D” was developed in just a few months. In the early spring of the year 1944, it was possible to begin the construction of an experimental boat of a new type. Continuing the established “tradition”, the first boat of the Tay-Gata type received its own designation “X-101”. Thus, the serial technology was supposed to receive names from "X-102" and further. The construction of the prototype continued until May, after which it was handed over to the customer for testing.
Unfinished boats in one of the factories. Photo Ww2db.com
Losing predecessors at maximum speed in all modes, the submarine "X-101" had a number of major advantages. The main advantage was considered significantly increased cruising range. The ability to travel up to 1000 nautical miles with one refueling allowed for long-term coastal patrols. In addition, with proper organization, new boats could participate in forays to enemy bases. The power of weapons in the form of two torpedoes "Type 97" even at the stage of preliminary work was considered sufficient, which is why the torpedo tubes did not undergo any refinement.
For various reasons, the tests of the first submarine were delayed. According to reports, its operation in the fleet began only at the end of May 1945. However, there could have been a transfer to the combat unit of an experimental boat, which was not originally intended to participate in the battles. In other words, the prototype, due to the lack of equipment, could urgently make a combat submarine.
Serial construction of submarines "Tay-Gata" started in the summer of 1944. The program of production of new technology involved several enterprises, but the bulk of the submarines were built at the Mitsubishi plant in Nagasaki and at the arsenal in Kure. Attraction of several enterprises was associated with the order volume. According to admirals, the Imperial fleet needed several hundred new ultra-small submarines. For this reason, as part of the order of new technology, several contracts were concluded with different factories.
The submarine on the stocks. Photo Ww2db.com
Until the beginning of September, several shipbuilding plants managed to manufacture and transfer 1945 boats to Koryu 115 to the customer. After the signing of the surrender of Japan, the US military gained access to defense enterprises, where, among other things, they were able to assess the scale of construction of ultra-small submarines. At the time of the surrender, the factories had 496 type “D” submarines in various stages of construction. Thus, only when fulfilling the existing orders, the Japanese fleet could receive more than six hundred units of new equipment.
It should be noted that not all submarines found in shipyards could be completed. At the final stage of the American war aviation regularly bombed Japanese military factories, including those related to the shipbuilding industry. A certain number of bombs "got" and ultra-small submarines. It is also necessary to recall the atomic bombing of Nagasaki, during which the whole city was seriously damaged, including the plant that built the submarines. However, later at this enterprise a considerable number of completely intact and suitable for completion of boats were found.
Exploitation
As far as we know, submarines of type “D” managed to take part only in the battles of Fr. Okinawa. For various reasons, the Imperial fleet did not get the opportunity to begin full-fledged operation of such equipment in order to patrol specified water areas and attack enemy ships. During combat work at Okinawa, submariners suffered noticeable losses. For some time, the submarine "Tay-Gata" used in parallel with the submarines of type "C".
At the end of January, 1945, six Koryu-type submarines, including the X-204, X-207 and X-208, were sent to the base located in Unten harbor (west coast of Okinawa). It was decided to send submarines under its own power, since their cruising range allowed access to the new base. The boats were accompanied by two vessels, which, if necessary, were to provide support. On the way to the new base, one of the submarines (supposedly “X-208”) collided with the escort ship. Tay-Gata damaged both torpedo tubes and ballast tanks. The damaged boat was left in the port of Sasebo, where the flotilla was supposed to go on the way to Okinawa. In February, it was repaired and sent to the place of service in early March.
Aerial view of the base in the harbor of Unten. Photo Combinedfleet.com
14 in March American intelligence officers based in Australia intercepted the Japanese fleet's cipher, from which it became aware of plans to deploy ultra-small submarines. Until the end of March, a transport vessel with four D-submarines and two C-type submarines was to arrive from Kure to Okinawa. After that, two types of 18 submarines were to be based in Okinawa. Another six “C” type boats were to be shipped to a new base in the first half of April.
23 March reconnaissance aircraft from the aircraft carrier USS Essex (CV-9) photographed the secret base of Japanese submarines in the harbor Unten. On the same day, the pilots of the 83 th air group attacked the base and flooded all the submarines standing there. During this raid, only submarines of type “C” were destroyed. Information about the losses "Tay-Gata" is missing.
In the evening of March 25, the X-209 and Ha-210 submarines leave the base in the Unten harbor with the task of searching and attacking enemy ships. At the base, they no longer returned. The exact fate of these boats remains unknown. Apparently, they were discovered and sank the American ships. The next day, the submarine "X-208" left the base, but soon she had to return. Shortly after going to sea, the power unit was damaged, which did not allow the task to continue.
April 1 began the battle for Okinawa, which lasted almost three months. In the course of this battle, the Japanese submariners made several attempts to attack the enemy, but they failed to achieve noticeable success. In this case, several raids resulted in the death of submarines. According to various sources, during the battle for Okinawa, the Imperial fleet lost at least five Koryu-type submarines. There was no success.
The battle for Okinawa turned out to be the first and the last major battle in which ultra-small D-type submarines could take part. Due to the quantitative and qualitative superiority of the enemy forces, primarily the anti-submarine defense, the Japanese submariners who were part of the crews of the Tei-Gata submarines could not fully use the advantages associated with the technical characteristics of the new technology.
Unfinished submarines, autumn 1945 of the year. Photo Ww2db.com
As a result, the submarines, which, as expected, will be able to protect the coast of Japan from attack, could not fulfill their task. Most of the submarines built and transferred to the fleet did not manage to take part in the battles. Some of this technology was destroyed during the bombing and shelling of the bases on which they were located. In addition, almost five hundred new submarines remained in the workshops of several factories in an unfinished state. Remained in the ranks of the "Koryu" and the unfinished boats eventually became trophies of the Americans. Specialists from the United States showed interest in this technique, but ultimately gave the go-ahead for the disposal of all captured ultra-small submarines.
Results of the project
From the point of view of success, the “D” project was very similar to the previous “C”. The purpose of these two developments was to update the design and equipment of the submarine, aimed at improving its characteristics. Indeed, the designers managed to complete the task. During the design work, they were able to improve some parameters and thus increase the overall potential of the boats.
The sailing range of nautical miles to 1000 made the Koryu type boats a unique type of equipment suitable for use in various operations. Nevertheless, the situation on the fronts was already developing not in the best way for Japan, which is why ultra-small submarines had to be used for other than its intended purpose. As a result, the results of combat use can not be called outstanding. For several months of service, the submarine type "D" did not sink a single enemy vessel. Own losses during the fighting in this case amounted to at least 5-7 submarines. A few more boats were lost as a result of the bombing.
It is easy to see that the submarines "Tay-Gata", which appeared by the middle of 1944, simply missed the war. An earlier appearance of such a technique in theory could change the situation, but the practice was less pleasant for the Japanese command. The project of the ultra-small submarine “D” added to the already long list of promising technology that could change the course of the war, but did not.
On the materials of the sites:
http://combinedfleet.com/
http://ww2db.com/
http://ibiblio.org/
http://modelist-konstruktor.com/
http://arsenal-info.ru/
http://navypedia.org/
General ideas
By the beginning of 1944, the situation in the Pacific theater of war of the Second World War had seriously changed. The Japanese command still could plan sabotage in the ports and on the bases of the enemy, but the situation forced him to begin preparations for the defense of his own coast. While maintaining the current trends in the foreseeable future, the issue of protecting the coast of Japan from American ships and landing forces became topical. It is the need to protect the coast and coastal waters was the main reason for the emergence of the project "D".
Unfinished submarine type "D" in one of the factories. Photo Ibiblio.org
In developing the Tay-Gata project, Japanese engineers decided to abandon the approach used earlier. Ultra-small submarines of types "A", "B" and "C" were a consistent development of the same design, carried out using different components and assemblies. Despite numerous improvements, the newer boats retained the old hull, which did not always have a positive effect on performance. In the new project “D” it was proposed to use some existing ideas, but to develop the submarine again.
The refusal of the old building was associated with some new requirements and with the inability to enter the necessary units in the existing volume. Increasing the size of the boat within reasonable limits, in turn, allowed the use of new components with the required characteristics. Thus, the increase in size and weight was accompanied by an increase in a number of important parameters. Thus, it was possible to increase the volume of fuel tanks and thereby provide a new increase in the cruising range.
Design
The submarine of type “D” had a total length of more than 26 m, the maximum diameter of the robust hull exceeded 2 m, the height of the structure (with a wheelhouse) reached 3 m. The increase in size compared to previous submarines led to an increase in displacement to 60 t in a submerged position. It was expected that a larger and heavier submarine with the help of new powertrain units would be able to retain the required characteristics.
The scheme of the submarine type "D". Figure Ibiblio.org
According to the results of testing and operation of ultra-small submarines of the previous types, it was decided to seriously rework the hull structure. To improve the basic characteristics, both the design itself and the layout of the robust case were changed. Now it began at a short distance from the bow, and a propeller and steering gear was located at its stern. The bow of the strong body had the shape of a truncated cone, the middle - the cylinder. Several tail compartments were also made in the form of cones of different heights and diameters. In the middle part of the hull was cutting. To improve seaworthiness, a narrow and long superstructure was fixed on the upper surface of a solid hull, forming a characteristic vertical nose.
Large openings for the installation of torpedo tubes were provided in the nasal wall of the strong hull. Two such devices were placed one above the other, their backs were located inside a robust case. To simplify the maintenance of equipment, the crew had access to the nose torpedo compartment and could from there control the work of weapons. Behind the compartment with torpedo tubes there was another habitable volume, under the floor of which were batteries. Under the wheelhouse, a relatively large central post was provided. The crew of the submarine of the type “Koryu” was to consist of five people, because of which it was necessary to significantly change the layout and size of the inhabited compartments.
Directly behind the central post was a diesel engine with a generator. Behind this compartment, a free volume was provided with part of the batteries. The running motor connected to the propeller shaft was located in the aft compartment. The “D” type boat had one propeller placed on the hull aft hull. On the case in front of the screw there were rudders and depth rudders.
View of the torpedo tubes. Photo Ww2db.com
Compartments durable hull divided by several bulkheads. To move from compartment to compartment, the crew had to use openings-hatches. Manhole covers, in order to save space, were not provided. Thus, the flooding of one of the compartments could lead to the ingress of water into the neighboring ones.
Inside the lightweight superstructure, as well as inside the robust hull, there were several ballast tanks, which allowed diving to the desired depth and balancing. Compressed air cylinders for the purging of tanks were distributed over the free volumes of the hull. For example, two such tanks were located next to the torpedo tubes.
Increasing the size of the hull allowed the use of a diesel engine with an output of 150 hp. The consequence of this was a reduction in the time required to fully charge existing batteries. Now this process took no more than 7-8 hours. The electric motor with power 500 hp was responsible for the movement. Apparently, the calculations showed that the preservation of the old 600-strong engine will not give any particular advantages, although it will affect the size and weight of the whole structure.
When moving on the surface, the submarine of the type “D” could reach a speed of no more than 10-12 nodes. Maximum speed under water did not exceed 16-18 nodes. Thus, at maximum speed, the new submarines were noticeably inferior to their predecessors. However, Japanese engineers managed to significantly increase the cruising range. When using a diesel engine and a speed of no more than 8 units on one refueling, you could go up to 1000 nautical miles. On 16 nodes under water, batteries provided a range of 125 miles. The strength of the hull was enough to dive to a depth of 100 m.
The armament of the new submarine was borrowed from the old ones. In the bow of the submarine were two torpedo tubes caliber 450 mm. The main armament of the boats "Koryu" were torpedoes "Type 97". Such weapon could reach speeds up to 45 nodes and deliver a combat unit with a weight of 5,5 kg to a range of 350 km. The torpedo tubes of the ultra-small submarine were made muzzle loading. Because of this, submarine ammunition consisted of only two torpedoes. To recharge before attacking new targets should return to the base.
Interior of the central post. Photo Ww2db.com
According to reports, the crew of the submarine "Tay-Gata" consisted of five people. A co-driver and a torpedo were added to the commander, helmsman, and motorist. The increase in crew led to the need for improvements in habitable volumes, but allowed to reduce the load on an individual submariner. It was assumed that five people will be able to work without any difficulty for several days, occasionally replacing each other. Estimated travel range in combination with the maximum estimated patrol time forced the designers to pay special attention to the physical capabilities of the crews.
The central post of the type “D” submarine was equipped with all the necessary equipment. Submariners were able to monitor the situation above the water and underwater with the help of a periscope and hydrophones. A compass and a number of other equipment were used for navigation. On several dashboards there was a set of various analog instruments and other types of indicators. The crew could monitor the operation of all systems, both instrumentally and visually. For example, the mechanic had access to both engines and could perform all operations for their maintenance.
Mass production
Despite the need for a lot of complex design work, the project “D” was developed in just a few months. In the early spring of the year 1944, it was possible to begin the construction of an experimental boat of a new type. Continuing the established “tradition”, the first boat of the Tay-Gata type received its own designation “X-101”. Thus, the serial technology was supposed to receive names from "X-102" and further. The construction of the prototype continued until May, after which it was handed over to the customer for testing.
Unfinished boats in one of the factories. Photo Ww2db.com
Losing predecessors at maximum speed in all modes, the submarine "X-101" had a number of major advantages. The main advantage was considered significantly increased cruising range. The ability to travel up to 1000 nautical miles with one refueling allowed for long-term coastal patrols. In addition, with proper organization, new boats could participate in forays to enemy bases. The power of weapons in the form of two torpedoes "Type 97" even at the stage of preliminary work was considered sufficient, which is why the torpedo tubes did not undergo any refinement.
For various reasons, the tests of the first submarine were delayed. According to reports, its operation in the fleet began only at the end of May 1945. However, there could have been a transfer to the combat unit of an experimental boat, which was not originally intended to participate in the battles. In other words, the prototype, due to the lack of equipment, could urgently make a combat submarine.
Serial construction of submarines "Tay-Gata" started in the summer of 1944. The program of production of new technology involved several enterprises, but the bulk of the submarines were built at the Mitsubishi plant in Nagasaki and at the arsenal in Kure. Attraction of several enterprises was associated with the order volume. According to admirals, the Imperial fleet needed several hundred new ultra-small submarines. For this reason, as part of the order of new technology, several contracts were concluded with different factories.
The submarine on the stocks. Photo Ww2db.com
Until the beginning of September, several shipbuilding plants managed to manufacture and transfer 1945 boats to Koryu 115 to the customer. After the signing of the surrender of Japan, the US military gained access to defense enterprises, where, among other things, they were able to assess the scale of construction of ultra-small submarines. At the time of the surrender, the factories had 496 type “D” submarines in various stages of construction. Thus, only when fulfilling the existing orders, the Japanese fleet could receive more than six hundred units of new equipment.
It should be noted that not all submarines found in shipyards could be completed. At the final stage of the American war aviation regularly bombed Japanese military factories, including those related to the shipbuilding industry. A certain number of bombs "got" and ultra-small submarines. It is also necessary to recall the atomic bombing of Nagasaki, during which the whole city was seriously damaged, including the plant that built the submarines. However, later at this enterprise a considerable number of completely intact and suitable for completion of boats were found.
Exploitation
As far as we know, submarines of type “D” managed to take part only in the battles of Fr. Okinawa. For various reasons, the Imperial fleet did not get the opportunity to begin full-fledged operation of such equipment in order to patrol specified water areas and attack enemy ships. During combat work at Okinawa, submariners suffered noticeable losses. For some time, the submarine "Tay-Gata" used in parallel with the submarines of type "C".
At the end of January, 1945, six Koryu-type submarines, including the X-204, X-207 and X-208, were sent to the base located in Unten harbor (west coast of Okinawa). It was decided to send submarines under its own power, since their cruising range allowed access to the new base. The boats were accompanied by two vessels, which, if necessary, were to provide support. On the way to the new base, one of the submarines (supposedly “X-208”) collided with the escort ship. Tay-Gata damaged both torpedo tubes and ballast tanks. The damaged boat was left in the port of Sasebo, where the flotilla was supposed to go on the way to Okinawa. In February, it was repaired and sent to the place of service in early March.
Aerial view of the base in the harbor of Unten. Photo Combinedfleet.com
14 in March American intelligence officers based in Australia intercepted the Japanese fleet's cipher, from which it became aware of plans to deploy ultra-small submarines. Until the end of March, a transport vessel with four D-submarines and two C-type submarines was to arrive from Kure to Okinawa. After that, two types of 18 submarines were to be based in Okinawa. Another six “C” type boats were to be shipped to a new base in the first half of April.
23 March reconnaissance aircraft from the aircraft carrier USS Essex (CV-9) photographed the secret base of Japanese submarines in the harbor Unten. On the same day, the pilots of the 83 th air group attacked the base and flooded all the submarines standing there. During this raid, only submarines of type “C” were destroyed. Information about the losses "Tay-Gata" is missing.
In the evening of March 25, the X-209 and Ha-210 submarines leave the base in the Unten harbor with the task of searching and attacking enemy ships. At the base, they no longer returned. The exact fate of these boats remains unknown. Apparently, they were discovered and sank the American ships. The next day, the submarine "X-208" left the base, but soon she had to return. Shortly after going to sea, the power unit was damaged, which did not allow the task to continue.
April 1 began the battle for Okinawa, which lasted almost three months. In the course of this battle, the Japanese submariners made several attempts to attack the enemy, but they failed to achieve noticeable success. In this case, several raids resulted in the death of submarines. According to various sources, during the battle for Okinawa, the Imperial fleet lost at least five Koryu-type submarines. There was no success.
The battle for Okinawa turned out to be the first and the last major battle in which ultra-small D-type submarines could take part. Due to the quantitative and qualitative superiority of the enemy forces, primarily the anti-submarine defense, the Japanese submariners who were part of the crews of the Tei-Gata submarines could not fully use the advantages associated with the technical characteristics of the new technology.
Unfinished submarines, autumn 1945 of the year. Photo Ww2db.com
As a result, the submarines, which, as expected, will be able to protect the coast of Japan from attack, could not fulfill their task. Most of the submarines built and transferred to the fleet did not manage to take part in the battles. Some of this technology was destroyed during the bombing and shelling of the bases on which they were located. In addition, almost five hundred new submarines remained in the workshops of several factories in an unfinished state. Remained in the ranks of the "Koryu" and the unfinished boats eventually became trophies of the Americans. Specialists from the United States showed interest in this technique, but ultimately gave the go-ahead for the disposal of all captured ultra-small submarines.
Results of the project
From the point of view of success, the “D” project was very similar to the previous “C”. The purpose of these two developments was to update the design and equipment of the submarine, aimed at improving its characteristics. Indeed, the designers managed to complete the task. During the design work, they were able to improve some parameters and thus increase the overall potential of the boats.
The sailing range of nautical miles to 1000 made the Koryu type boats a unique type of equipment suitable for use in various operations. Nevertheless, the situation on the fronts was already developing not in the best way for Japan, which is why ultra-small submarines had to be used for other than its intended purpose. As a result, the results of combat use can not be called outstanding. For several months of service, the submarine type "D" did not sink a single enemy vessel. Own losses during the fighting in this case amounted to at least 5-7 submarines. A few more boats were lost as a result of the bombing.
It is easy to see that the submarines "Tay-Gata", which appeared by the middle of 1944, simply missed the war. An earlier appearance of such a technique in theory could change the situation, but the practice was less pleasant for the Japanese command. The project of the ultra-small submarine “D” added to the already long list of promising technology that could change the course of the war, but did not.
On the materials of the sites:
http://combinedfleet.com/
http://ww2db.com/
http://ibiblio.org/
http://modelist-konstruktor.com/
http://arsenal-info.ru/
http://navypedia.org/
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