The Imperial Japanese Navy’s fleet of battleships had proven highly successful in 1905—the last year of the Russo-Japanese War—culminating in the destruction of the Russian Baltic Fleet at the Battle of Tsushima. In the aftermath, the Japanese Empire immediately turned her focus to the two remaining rivals for imperial dominance in the Pacific Ocean: Britain and the United States. Satō Tetsutarō, a Japanese Navy admiral and military theorist, speculated that conflict would inevitably arise between Japan and at least one of their two main rivals. To that end, he called for the Japanese Navy to maintain a fleet with at least 70% as many capital ships as the US Navy. This ratio, Sato- theorized, would enable the Imperial Japanese Navy to defeat the US Navy in a decisive battle in Japanese waters in any eventual conflict. To that end, the 1907 Imperial Defense Policy called for the construction of a battle fleet of eight modern battleships—20,000 long tons (20,000 t) each—and eight modern armored cruisers—18,000 long tons (18,000 t) each—to match the US Navy. This was the genesis of the Eight-Eight Fleet Program, the development of a cohesive battle line of sixteen capital ships.
The launch of HMS Dreadnought in 1906 by the Royal Navy “revolutionized capital ship design”, and complicated Japan’s plans. Displacing 17,900 long tons (18,200 t) and armed with ten 12-inch (30 cm) guns, Dreadnought rendered all existing battleships obsolete by comparison. The launch of the battlecruiser HMS Invincible the following year was a further setback for Japan quest for parity. When Japan’s two new Satsuma-class battleships and two Tsukuba-class armored cruisers, launched by 1911, were outclassed by their British counterparts, the Eight-Eight Fleet Program was restarted.
The first battleships built for the Eight-Eight Fleet Program were the two dreadnoughts of the Kawachi class, ordered in 1907 and laid down in 1908. In 1910, the Navy put forward a request to the Diet of Japan (parliament) to secure funding for the entirety of the program at once. Because of economic constraints, the proposal was cut first by the Navy Ministry to seven battleships and three battlecruisers, then by the cabinet to what became the Japanese Naval Emergency Expansion bill, authorizing the construction of four battlecruisers (the Kongo- class) and one battleship, later named Fuso.
Originally intended as sister ships of the preceding Fusō class, the Ise-class battleships of the Imperial Japanese Navy were considered sufficiently different to warrant separate classification.
Among the differences were a shorter foredeck, a more closely grouped secondary armament (with the majority of the forward guns set further astern than in the Fusōs), a different arrangement of the primary turrets (though the cumbersome six-twin arrangement was retained), more closely spaced funnels and uptakes, and eventually rear flightdecks.
Like most if not all battleships of their era, they retained the soon-to-be outmoded casemated secondary armament, the forward guns of which often proved useless in any kind of seaway, and like all Japanese warships of the period, these vessels still relied on mixed (i.e. coal and oil) firing for their boilers.
The Nagato-class battleships were two battleships (Nagato and Mutsu) of the Imperial Japanese Navy. The name Nagato comes from the Nagato province. They were the first battleships to be built entirely in Japan. They were the first battleships in the world to mount 16 inch (410 mm) guns and were considered as the Japanese navy equivalents of the British Navy’s ‘Queen Elizabeth’ class battleships. At the time of their completion in 1920–21, their armament, armor, and speed made them the most powerful capital ships in the world
As Japanese military and naval authorities looked out on the world in the early twenties, therefore, they could be pardoned for thinking that the military, political, and even economic tides seemed to be running against them everywhere except on the adjacent continent of Asia. For four years, as warfare had raged all across Europe, Japanese warships had patrolled hundreds of thousands of square miles of the Pacific and Indian Oceans without let or hindrance. Japan had cooperated with Britain in successfully besieging the German bastion at Tsingtao, and at the behest of Whitehall the Imperial Japanese Navy had steamed out into the Pacific to help in the search for Maximilian Graf von Spee’s squadron, using the cruise as a pretext to seize German-held islands in Oceania. In a third “unheralded” campaign, a division of Japanese destroyers entered the eastern Mediterranean in the spring of 1917 to help hard-pressed British antisubmarine forces battle the German U-boats. None had gone to the bottom under Japanese depth charges, but Tokyo had proved to be a loyal partner in the Anglo-Japanese alliance. Now Japan was once again to be compressed by the great powers into a very narrow sphere of operations and influence. It was Asia’s great indigenous power, but the rest of the world seemed determined to rob it of its rightful destiny.
These disheartening developments fractured the Imperial Japanese Navy into what would become “Fleet” and “Treaty” factions. The former, led by senior Admiral Kato¯ Kanji and including “Japan’s Mahan,” Satō Tetsutarō, insisted the nation must push ahead vigorously with its massive eight-eight construction program. Others argued for a more cautious and fiscally realistic course. Should the Americans and British continue to outbuild the Japanese fleet in terms of sheer numbers, Japan must respond with fewer but finer and more powerful capital ships. Initially, four fast battle cruisers of 41,400 tons mounting 16-inch guns would be laid down together with four 47,500-ton monster battleships carrying ten 18-inch guns apiece. After rejecting an eight-eight bill, a reluctant parliament (the Diet) approved the four-four plan. There were several good reasons to do so. Tokyo was well aware of postwar Anglo-American tensions over the Middle East; surely, the rivalry would resume in China as well once peace came again. One scholar of the period has concluded that “caution and perhaps confidence born of successful maneuvering in domestic politics” inclined Japanese political leaders to the belief that in East Asian affairs, at least, Tokyo might become an honest broker and arbiter between Washington and London. The Fleet faction, however, clung steadfastly to its eight-eight vision as a solution to all Japan’s problems. “Big guns” and “big ships” guarding the approaches to the Home Islands were the keys to national survival. Satō Tetsutarō and his colleagues at the Naval Staff College had long since concluded that sixteen mighty capital ships would ensure Japan of a 70 percent parity with any attacking fleet, which would provide the margin of victory. The 70 percent ideal was itself expressed in a variety of ways. Before the opening of the Panama Canal 70 percent meant that either the United States or Germany could afford to station only half their fleets in the Pacific because of persistent tensions in Atlantic waters. Thus, 70 percent would in fact become a seven-to-five ratio in Japan’s favor. With the end of the Great War, the opening of the Panama Canal, and the advent of the submarine, Japanese planners estimated that although an enemy (that is, the United States) could dispatch its entire navy toward Japan, determined submarine attacks would so whittle down the advancing fleet that by the time the climactic battle was fought, the ratio would be no worse than seven to seven. Anything less than 70 percent parity with the Western navies, however, was unacceptable. In July 1920, after nearly a decade of unstinting lobbying, the Fleet faction finally won out when the Diet reversed the earlier four-four legislation and passed an eight-eight bill.
But even with sixteen capital ships on hand, the great American naval buildup threatened after 1916 would overwhelm Japan’s ability to maintain 70 percent parity, particularly if there arose a combination of sea powers against Nippon. Here was where the prospect of losing the British alliance became so fearsome and the need to build capital ships of superior size and capability so critical. Moreover, Japanese strategy by this time was utterly divided. The 1907 Imperial National Defense Policy, which was never significantly altered, formally designated Russia as Japan’s prime hypothetical enemy, “and the Army’s forward position on the Asian mainland was made Japan’s basic strategy.” The army would almost certainly require some naval assistance to fulfill its mission whether against Russia or China. At the same time the navy was allowed to identify the United States as its chief opponent and successfully resisted efforts to create a single national command structure under army control. Japan thus might well find itself fighting a two-front war with wholly inadequate resources and a chaotic command structure.