Recently, the Ministry of defense of the Republic of Korea has explicitly proposed for the first time the construction of a medium-sized ballistic missile nuclear submarine with an underwater displacement of 4000 tons in the newly released “mid-term national defense plan for 2021-2025”, which has aroused great concern from the outside world. As we know, the technical threshold for nuclear submarines is quite high. So far, only the United States, Russia, China, France and the United Kingdom, the five permanent members of the United Nations, have the strength to design and build nuclear submarines in bulk. Although India launched the first domestic nuclear submarine “destroyer” in 2009, it did not come into service until 2016, and the construction of follow-up ships is still far away. Therefore, India can only be regarded as “stepping into the threshold of nuclear submarine countries with one foot”, but not a real member of “nuclear submarine club”. In the past 30 years, Korea has made great progress in the construction of nuclear submarines. The picture shows South Korea’s “anchanghao” class ballistic missile submarine < / P > < p > the South Korean navy has a very clear target and opponent in the development of surface ships and submarine equipment, which is the Japanese Maritime Self Defense Force. Due to the long-standing dispute between South Korea and Japan over the territory and territorial waters of Dokdo (known as “Takeshima” in Japan) and the weakness of the navy of the Korean people’s army, the South Korean navy has always regarded the Japanese Maritime Self Defense Force as the most threatening potential opponent. This attitude is reflected in the equipment construction of the South Korean navy, which forms a seemingly simple and crude principle: the warships owned by Japan’s Maritime Self Defense Force should also be owned by the Korean navy, and there should be bigger ones. And the South Korean Navy wants more ships that Japan’s Maritime Self Defense Forces don’t have. Therefore, we can see that in the past 30 years, the South Korean navy and the Japanese Maritime Self Defense Force have launched a “tacit” naval arms race: the Japanese Maritime Self Defense Force owned the first “King Kong” class aegis missile destroyer in 1993, and the South Korean Navy made every effort to obtain the first “Shizong king” class aegis missile destroyer in 2008, Moreover, the tonnage and the number of vertical launching units far exceed the former. Similarly, after the Japanese Maritime Self Defense Force “Dawu” class amphibious dock landing ship came into service in 1998, the South Korean navy in 2007 was equipped with the “Dokdo” class amphibious assault ship with more powerful tonnage and combat power. However, due to the gap in comprehensive national strength, the construction and service of large-scale surface warships of the South Korean navy are always “loud thunder and little rain”, which can not compete with Japan’s Maritime Self Defense Force for a long time. For example, “Shizong king” class aegis missile destroyers were originally planned for six, but only three were built and put into service. “Dokdo” class amphibious assault ships were originally planned for four, which were also cut off. However, in the long-term and steady development plan of warships, Japan’s self defense force has always maintained a leading position over the South Korean navy. After having four “King Kong” class and two “aidang” class aegis missile destroyers, it will add two “Maya” class aegis missile destroyers, twice as many as “Shizong king” class aegis missile destroyers. Then, the gap between South Korea and Japan on conventional submarines is more obvious than that on surface ships. The nine Chang Pao Gao class conventional submarines and the nine sun yuan I class AIP submarines in active service of the South Korean Navy were all built by importing technology from Germany. The former is 209 / 1400, and the latter is 214. The third generation of “anchanghao” class AIP submarine with an underwater displacement of 3700 tons has only been built and launched, and is expected to be delivered to the South Korean Navy this year. In contrast, there are 21 conventional submarines in Japan’s maritime self defense force, including 10 Canglong class AIP submarines with a displacement of 4200 tons and 11 “tide friendly” class conventional submarines with underwater displacement of 3900 tons. Not only does the number exceed that of the South Korean navy, but the tonnage of the conventional submarines in active service of the Japanese maritime self defense force is generally larger than that of the former’s latest “anchanghao” class AIP submarine. Moreover, Japan’s defense ministry is still developing the latest generation of 29ss AIP submarines. Although the tonnage has not increased significantly compared with the “Canglong” class, it claims to build the “quietest” submarine in the world. It can be seen that the overall technical performance and strength of 29ss AIP submarine will reach a new height. In this case, the South Korean navy has been unable to continue to compete with Japan’s Maritime Self Defense Force in the field of conventional submarines. Therefore, the South Korean navy has thought of developing nuclear submarines. Because Japan is restricted by various aspects, it can not and dare not own nuclear powered ships, while South Korea does not. Moreover, the nuclear submarine is the submarine that “does not rely on air navigation” in the real sense. Its greater underwater speed, almost unlimited underwater endurance and combat power are far more than the ordinary conventional submarine and AIP submarine. Therefore, the South Korean Navy hopes to have a type of 4000 ton medium-sized nuclear submarine to offset the number advantage of “Canglong” class of Japanese Maritime Self Defense Force and the new generation of 29ss type AIP submarines, so as to form a more balanced situation of underwater combat forces of the two countries. Since the South Korean navy has made up its mind to build and equip nuclear submarines, there is no doubt that the South Korean Navy should learn from the successful experiences and lessons of the five major countries of “nuclear submarine club” and India. The author believes that the development of nuclear submarines in the United States, the Soviet Union / Russia, China, Britain, France and India can be roughly divided into three modes. The United States, the Soviet Union / Russia, China, the United Kingdom and other four countries adopt the same model, that is to build the attack type nuclear submarine first, and carry out the research and development of submarine launched ballistic missile at the same time, including the design and development of conventional ballistic missile submarine. After the nuclear submarine and submarine launched ballistic missile technology have reached a certain degree of maturity, we will combine the two to develop a ballistic missile nuclear submarine with strategic strike capability. < / P > < p > France is different. Due to the late start of development and the technical blockade of the United States, France started with ballistic missile nuclear submarines from the beginning, and embarked on a road of independent research and development of nuclear submarines. Of course, in order to ensure the smooth completion of the research and development of submarine launched ballistic missiles, France has also refitted a conventional ballistic missile submarine. After four “formidable” class ballistic missile nuclear submarines were put into service, France began to build the first attack type nuclear submarine “Ruby” in 1976. Up to now, the French Navy’s “Ruby” class attack nuclear submarine still maintains the record of the world’s smallest nuclear submarine with an underwater displacement of 2670 tons. < p > < p > the development of nuclear submarines in India was much later than that in the five countries of “nuclear submarine club”, and the research and development of related technologies was only started in 1978. After that, driven by many factors, such as leasing Russian nuclear submarines and obtaining nuclear reactors from Russia, India’s first domestic nuclear submarine “destroyer” started construction in 1998, launched in 2009, and put into service in 2016. < p > < p > for India, the cost of nuclear submarines is very high. The cost of the “destroyer” has reached a staggering US $2.9 billion, while the US Navy’s “Virginia” class attack nuclear submarine submarine is only $1.78 billion. Coupled with the technical difficulties, it is doomed to be unable to build in large quantities like the five countries of “nuclear submarine club”. < / P > < p > for the South Korean navy, the above three development models have their own advantages and disadvantages. However, on the whole, the Indian model is more suitable for the South Korean navy to learn from and learn from. After all, the South Korean navy can not afford to build and equip more nuclear submarines. Then, it is more necessary to integrate more weapon equipment and operational purposes in the design of type 1 nuclear submarine. In addition, similar to India, the South Korean army has basically established a relatively complete ballistic missile and cruise missile equipment system through a series of R & D plans such as “basaltic” 1 / 2 / 3 / 4. The “submarine launched missiles” of the “South Korean army” can be used to develop the “submarine launched missiles” of the “South Korean navy”. In addition, the South Korean navy can also use the new generation of “anchanghao” class AIP submarine as the test platform to more steadily promote the research and development of submarine launched missile technology. < p > < p > after selecting the development mode, the South Korean navy has to face a more difficult problem, that is, how to obtain nuclear submarine technology from a certain country, especially the most critical submarine nuclear reactor technology, at the lowest cost and in the shortest time. It is with the help of Russia that India completed the design and construction of domestic nuclear submarines, which is also worth imitating for the South Korean navy. Therefore, the South Korean navy is likely to turn to Russia for the development of nuclear submarines. After all, the two countries have maintained exchanges and cooperation in military technology. Moreover, the Russian Navy launched the “Sarov” submarine as early as 2009, which is in line with the needs of the South Korean navy. This mysterious technology verification boat is called “AIP submarine equipped with nuclear reactor”, which is equipped with diesel engine and small nuclear reactor at the same time. When sailing on the surface, the “Sarov” submarine uses diesel engine to propel; while in the underwater diving, “Sarov” submarine uses a small nuclear reactor to charge the battery as the propulsion power. < p > < p > compared with the nuclear submarine which relies on the nuclear reactor for propulsion and power supply, the technical threshold and difficulty of the “Sarov” submarine are relatively lower; compared with the conventional AIP submarine using stirling engine and fuel cell, the “Sarov” submarine has higher speed and underwater endurance comparable to that of a nuclear submarine. Moreover, the South Korean navy can avoid the risk of “nuclear technology proliferation” if it gets help from Russia in the name of AIP submarine technology. < / P > < p > if the South Korean navy can obtain the technology of the “Sarov” submarine, it can completely carry out the research and development of a new generation of nuclear submarine on the basis of the “anchanghao” class AIP submarine, and increase the cabin to accommodate multiple vertical launching units and nuclear reactors for launching submarine launched ballistic missiles and cruise missiles. Of course, the South Korean navy may also seek foreign aid from other countries, including France and India. However, the French see money again, and are unlikely to transfer the soon retired “Ruby” class attack type nuclear submarine technology to South Korea. As for India, its own nuclear submarine technology is not very reliable, let alone help South Korea build nuclear submarines. < p > < p > at present, South Korea has successfully developed the “basaltic” – 4 ballistic missile with a range of 800 km with a 2-ton warhead. If it is replaced by a 500 kg warhead, the range will be at least 1200 km. If the nuclear submarine carries the missile, it will become a “strategic nuclear submarine” with unique Korean characteristics, which can form a non nuclear strategic deterrent to several neighboring powers. Together with the “anchanghao” class conventional ballistic missile submarine, South Korea’s underwater deterrent power has been greatly enhanced, which will also have an important impact on the strategic balance in East Asia.