In 1576, the daimyo Oda Nobunaga commissioned six iron-covered warships known as Oatakebune, predating the first Western ironclads by nearly three centuries. This early technological leap occurred during the Warring States period when feudal rulers built vast coastal navies of several hundred ships to vie for supremacy. Yet, for over two hundred years beginning in the 1640s, Japan enforced a policy of seclusion called sakoku, forbidding contact with the outside world and prohibiting the construction of ocean-going ships on pain of death. The only exception was trade with the Dutch through the port of Nagasaki, where the study of Western sciences, known as rangaku, allowed Japan to remain aware of naval sciences like cartography and optics. This isolation led to the loss of any naval and maritime traditions the nation had previously possessed, leaving the country with an antiquated navy when Commodore Matthew Perry forced Japan open to trade in 1854. The shogunate had to scramble to build coastal defenses, acquiring field guns and mortars, and even constructing the Sōshun Maru, a small twin-mast military vessel with 22 oars and six Japanese-made smoothbore guns, to protect Edo Bay. The Morrison incident of 1837 and the news of China's defeat during the Opium War eventually led the shogunate to repeal the 1825 law to repel foreign ships, recognizing that traditional ways would not be sufficient to repel further intrusions.
The Meiji Restoration and Centralization
The Meiji Restoration in 1868 led to the overthrow of the shogunate, but the new government initially lacked a centralized navy, administering only the Tokugawa vessels captured during the early phase of the Boshin War. Tensions between the former ruler and the restoration leaders resulted in the Boshin War, which lasted from January 1868 to June 1869. The early part of the conflict largely involved land battles, with naval forces playing a minimal role in transporting troops from western to eastern Japan. Only the Battle of Awa on the 28th of January 1868 was significant, proving one of the few Tokugawa successes in the war. Admiral Enomoto Takeaki, the admiral of the shogun's navy, refused to surrender all his ships, remitting just four vessels, and escaped to northern Honshu with the remnants of the shogun's navy, including eight steam warships and 2,000 men. He fled to Hokkaido, where he established the breakaway Republic of Ezo on the 27th of January 1869. The new Meiji government dispatched a military force to defeat the rebels, culminating with the Naval Battle of Hakodate in May 1869. The imperial side took delivery of the French-built ironclad Kotetsu in February 1869 and used it decisively towards the end of the conflict. In 1871, the domains were abolished altogether, and the centralization of the navy began with the domains donating their forces to the central government. This marked the institutional beginning of the Imperial Japanese Navy, as the government finally boasted a centrally controlled navy. In February 1872, the Ministry of War was replaced by a separate Army Ministry and Navy Ministry, and in October 1873, Katsu Kaishu became Navy Minister, recommending the rapid centralization of all naval forces under one agency.
In 1870, an Imperial decree determined that Britain's Royal Navy should serve as the model for development, replacing the Netherlands navy. A thirty-four-man British naval mission, headed by Lt. Comdr. Archibald Douglas, arrived in Japan in 1873 and remained until 1879, substantially advancing the development of the navy and firmly establishing British traditions within the Japanese navy from matters of seamanship to the style of its uniforms. The navy sent 16 trainees abroad for training in naval sciences, including Heihachiro Togo, who would later become a legendary admiral. Ships such as the Chiyoda and the Choshu were built in British shipyards, and they were the first warships built abroad specifically for the Imperial Japanese Navy. The navy's first major test came during the First Sino-Japanese War, which began in 1894. The Japanese naval leadership was generally cautious and even apprehensive at the prospect of hostilities with China, as the navy had not yet received several modern warships that had been ordered in February 1893. Japan's main strategy was to swiftly obtain naval superiority, as this was critical to the success of operations on land. On the 17th of September 1894, the Japanese encountered the Beiyang Fleet off the mouth of the Yalu River. The Beiyang Fleet was crippled during the ensuing battle, in which the Chinese lost eight out of 12 warships. The Chinese subsequently withdrew behind the Weihaiwei fortifications, but they were then surprised by Japanese troops, who had outflanked the harbor's defenses in coordination with the navy. The remnants of the Beiyang Fleet were destroyed at Weihaiwei. Although Japan had emerged victorious at sea, the two large German-made Chinese ironclad battleships, Dingyuan and Zhenyuan, had remained almost impervious to Japanese guns, highlighting the need for bigger capital ships in the Imperial Japanese Navy.
The Russo-Japanese War and Tsushima
Following the war against China, Japan was pressured into renouncing its claim to the Liaodong Peninsula in the Russian-led Triple Intervention. The cession of the Liaodong Peninsula was seen as a humiliation by the Japanese political and military leadership, and Japan began to build up its military strength in preparation for future confrontations. In 1895, Yamamoto Gombei was assigned to compose a study of Japan's future naval needs, theorizing that Japan should have a force of at least six large battleships, supplemented by four armored cruisers of at least 7,000 tons. This led to the concept of a Six-Six Fleet, calling for a fleet consisting of six battleships and six armored cruisers. The program for a 260,000-ton navy, to be completed over a ten-year period, was approved by the cabinet in late 1895 and funded by the Diet in early 1896. The program was largely financed via indemnities secured from the Chinese after the First Sino-Japanese War. In 1902, Japan formed an alliance with Britain, which stipulated that if Japan went to war in the Far East and that a third power entered the fight against Japan, then Britain would come to the aid of the Japanese. The new fleet first saw action with the onset of the Russo-Japanese War. At the Battle of Tsushima, Admiral Togo led the Japanese Grand Fleet into the decisive engagement of the war. The Russian fleet was almost completely annihilated in a lopsided battle; out of 38 Russian ships, 21 were sunk, seven captured, and six disarmed. 4,545 Russian servicemen were killed and 6,106 taken prisoner. Conversely, the Japanese only lost 116 men and three torpedo boats. These victories broke Russian naval strength in East Asia, and triggered waves of mutinies in the Russian Navy at Sevastopol, Vladivostok, and Kronstadt, peaking in June with the Potemkin uprising, which contributed to the Russian Revolution of 1905. The victory at Tsushima significantly elevated the stature of the Japanese navy at home and abroad.
The Washington Treaty and Naval Aviation
In the years following the end of the First World War, the naval construction programs of the world's three greatest naval powers had threatened to set off a new potentially dangerous and expensive naval arms race. Negotiations between the three powers resulted in the Washington Naval Treaty of 1922, which became one of history's most effective arms reduction programs, setting up a system of ratios between the five signatory powers. The United States and Britain were each allocated 525,000 tons of capital ships, Japan 315,000, and France and Italy 175,000, corresponding to ratios of 5:3:1.75. The treaty's signatories also agreed to a ten-year moratorium on battleship construction, though replacement of battleships reaching 20 years of service was permitted. Maximum displacement limits of 35,000 tons per ship, and a prohibition on arming ships with guns larger than 16 inches, were also set. Japan's naval armament proponents were outraged by these limitations, as they limited Japanese naval tonnage well behind that of its foremost rivals at sea. However, the Japanese ultimately concluded that unfavorable tonnage limitations were preferable to an unrestricted arms race with the industrially dominant United States. Despite the treaty, Japan took the lead in many areas of warship development. In 1921, it launched the Hosho, the first purpose-built aircraft carrier in the world to be completed, and subsequently developed a fleet of carriers that would be one of the most powerful in the world by the early 1940s. The British Sempill Mission, led by Captain William Forbes-Sempill, arrived in Japan in November 1921 and stayed for 18 months, bringing well over a hundred British aircraft comprising twenty different models to Kasumigaura. The mission brought the plans of the most recent British aircraft carriers, such as HMS Argus and HMS Hermes, which influenced the final stages of the development of the Japanese carrier Hosho. By the time the mission's last members had returned to Britain, the Japanese had acquired a reasonable grasp of the latest aviation technology and taken the first steps toward building an effective naval air force.
The Doctrine of Decisive Battle
Throughout the 1930s, Japanese politics became increasingly dominated by militaristic leaders who prioritized territorial expansion, and who eventually came to view the United States as Japan's main obstacle to achieving this goal. Japanese naval planners subscribed to a doctrine of decisive battle, or Kantai Kessen, which stipulated that Japan's path to victory against a peer adversary at sea required the IJN to comprehensively destroy the bulk of an enemy's naval strength in a single, large-scale fleet action. Derived from the writings of Satou Tetsutarou, who was doubtless influenced by Alfred T. Mahan, Kantai Kessen was the basis of Japan's demand for a 70% ratio at the Washington Naval Conference. The United States would be able to enforce a 60% ratio thanks to having broken the Japanese diplomatic code and being able to read signals from its government to its negotiators. In the specific case of a hypothetical war with the United States, this decisive battle doctrine required the U.S. Navy to sail in force across the Pacific, during which it would be harassed and degraded by Japanese submarines, and then engaged and destroyed by IJN surface units in a decisive battle area somewhere in waters close to Japan. Japan's numerical and industrial inferiority to rivals such as the United States led the Japanese leadership to pursue technical superiority, qualitative superiority, and aggressive tactics. However, these calculations failed to account for the type of war Japan would be fighting against an enemy like the U.S. Japan's opponents in any future Pacific War would not face the political and geographical constraints that adversaries in previous wars did, and Japanese strategic planning did not properly account for serious potential losses in ships and crews. A consistent weakness of Japanese warship development was the tendency to incorporate excessive firepower and engine output relative to ship size, which was a side-effect of the Washington Treaty limitations on overall tonnage. This led to shortcomings in stability, protection, and structural strength.
The Circle Plans and the Road to War
In response to the London Treaty of 1930, the Japanese initiated a series of naval construction programs known unofficially as the maru keikaku, or Circle plans. Between 1930 and the outbreak of the Second World War, four of these Circle plans were drawn up: in 1931, 1934, 1937, and 1939. The Circle One plan, approved in 1931, provided for the construction of 39 ships to be laid down between 1931 and 1934, centering on four of the new Nagato-class battleships, and the expansion of the Naval Air Service to fourteen air groups. However, plans for a second Circle plan were delayed by the capsizing of the Tomozuru and heavy typhoon damage to the Fourth Fleet, which revealed that the fundamental design philosophy of many Japanese warships was flawed. These flaws included poor construction techniques and structural instability caused by mounting too much weaponry on too small of a displacement hull. In 1934, the Circle Two plan was approved, covering the construction of 48 new warships, including the Fuso-class battleships and two aircraft carriers, the Akagi and the Kaga. The plan also continued the buildup in naval aircraft and authorized the creation of eight new Naval Air Groups. With Japan's renunciation of previously signed naval treaties in December 1934, the Circle Three plan was approved in 1937, marking Japan's third major naval building program since 1930. Circle Three called for the construction of new warships that were free from the restrictions of previous naval treaties over a period of six years. New ships would concentrate on qualitative superiority in order to compensate for Japan's quantitative deficiencies compared to the United States. While the primary focus of Circle Three was to be the construction of two super-battleships, the Yamato and the Musashi, it also called for building the two IJN Kongou-class battlecruisers, along with sixty-four other warships of other categories. In 1938, with Circle Three under way, the Japanese began to consider preparations for a fourth naval expansion project, which was scheduled for 1940. With the American Naval Act of 1938, the Japanese accelerated the Circle Four six-year expansion program, which was approved in September 1939. Circle Four's goal was doubling Japan's naval air strength in just five years, delivering air superiority in East Asia and the western Pacific.
The Pacific War and the End of the IJN
To effectively combat the numerically superior U.S. Navy, the Japanese had devoted a large amount of resources to create a force of superior quality. Crucially, relying heavily on the use of aggressive tactics which stemmed from Mahanian doctrine and the concept of decisive battle, Japan did not invest significantly in capabilities needed to protect its long shipping lines against enemy submarines. In particular, Japan under-invested in the vital area of antisubmarine warfare, both escort ships and escort carriers, and in the specialized training and organization to support it. The IJN fielded limited land-based forces, including professional marines, marine paratrooper units, anti-aircraft defense units, installation and port security units, naval police units, and ad-hoc formations of sailors pressed into service as naval infantry. The origins of the IJN date back to early interactions with nations on the Asian continent, beginning in the early feudal period and reaching a peak of activity during the 16th and 17th centuries at a time of cultural exchange with European powers during the Age of Discovery. After two centuries of stagnation during the country's ensuing seclusion policy under the shogun of the Edo period, Japan's navy was comparatively antiquated when the country was forced open to trade by American intervention in 1854. This eventually led to the Meiji Restoration. Accompanying the re-ascendance of the Emperor came a period of frantic modernization and industrialization. The IJN saw several successes in combat during the early twentieth century, sometimes against much more powerful enemies, such as in the Sino-Japanese War and the Russo-Japanese War, before being largely destroyed in World War II. The Imperial Japanese Navy was the third largest navy in the world by 1920, behind the Royal Navy and the United States Navy. It was supported by the Imperial Japanese Navy Air Service for reconnaissance and airstrike operations from the fleet. It was the primary opponent of the Western Allies in the Pacific War. The IJN was dissolved following Japan's surrender in World War II in 1945, and the Japan Maritime Self-Defense Force was formed between 1952 and 1954 after the dissolution of the IJN.