Yamamoto Isoroku (1884-1943) was Commander-in-chief of combined Japanese fleet, who was Japan's greatest naval strategist in World War II.
Yamamoto Isoroku, "the Nelson of the Japanese navy," was originally born Takano Isoroku, sixth son of an impoverished schoolteacher, Takano Teikichi, and his second wife Mineko, on April 4, 1884. Isoroku belonged to the Echigo clan, an old tough warrior people who had resisted the unification of Japan under the Meiji emperor. His father gave him the name Isoroku (meaning 56 in Japanese) as he was that age when his son was born in the small village of Kushigun Sonshomura on a bleak northern island that produced many Japanese sailors. Soon after his birth, his father became headmaster of the primary school in the nearby market town of Nagaoka.
At age 16, after taking competitive examinations, Isoroku enrolled in the Naval Academy at Etajima, off the shore of Hiroshima. There he spent three years, combining study with rigorous physical training. After that, he spent a year on a square-rigged windjammer. Graduating in 1904 as seventh in his class, he fought against Russia's Baltic Fleet at Tsushima, a strait between Japan and Korea, in an engagement recognized by historians as "one of the most decisive naval actions in history." As an ensign on the cruiser Nisshin, part of the protective screen for Admiral Togo Heihachiro's flagship Mikasa, Isoroku saw closeup the tactics of one of the world's greatest admirals. From Togo, he learned one thing above all: the need for surprise in battle. In a letter to his family, the young seaman described a major mishap:
When the shells began to fly above me I found I was not afraid. The ship was damaged by shells and many were killed. At 6:15 in the evening a shell hit the Nisshin and knocked me unconscious. When I recovered I found I was wounded in the right leg and two fingers of my left hand were missing. But the Russian ships were completely defeated and many wounded and dead were floating on the sea.
Between 1904 and the outbreak of World War I, Isoroku went on training cruises to Korea and China, traveled to the west coast of the United States, and toured every major port in Australia. In 1913, he was sent to the Naval Staff College at Tsukiji, a prerequisite for high command. Upon graduation in 1916, he was appointed to the staff of the Second Battle Squadron.
That same year, at age 30, Isoroku—now a lieutenant commander—was adopted by the wealthy and socially prestigious Yamamoto family. Such adoptions were a common practice in Japan: families lacking a male heir sought to keep the lineage from dying out. As Isoroku's parents had died several years earlier, he felt he could accept the Yamamoto's generous invitation. At a formal ceremony in a Buddhist temple, he took on the family name, which means "Base of the Mountain."
At age 30, Yamamoto married Reiko Mihashi, daughter of a dairy farmer from his own province and a woman who bore him four children. Although he engaged in intensive Buddhist meditation, he made no secret of his relationships with "ladies of the night." A talented calligrapher, he would decorate the geisha houses of his past and current mistresses, and lived far beyond his means, earning a second income from his skill at bridge and poker. He once said, "If I can keep 5,000 ideographs in my mind, it is not hard to keep in mind 52 cards."
In April of 1919, Yamamoto began two years of study at Harvard University, where he concentrated on the oil industry—the lifeblood of any modern navy. Returning with the rank of commander in July of 1921, he was appointed instructor at the naval staff college in Tokyo. In June of 1923, he became captain of the cruiser Fuji.
Yamamoto received his first major command when in September of 1924 he was sent to the new air-training center at Kasumigaura, 60 miles northeast of Tokyo, where at age 40 he took flying lessons. Within three months, he was director of studies. Yamamoto's handpicked pilots became an élite corps, the most sought-after arm of the Japanese navy. From January of 1926 to March of 1928, he was naval attaché to the Japanese embassy in Washington, there to investigate America's military might.
Historian Gordon W. Prange describes Yamamoto at the height of his powers as:
a man short even by Japanese standards (five feet three inches), with broad shoulders accentuated by massive epaulets and a thick chest crowded with orders and medals. But a strong, commanding face dominates and subdues all the trappings. The angular jaw slants sharply to an emphatic chin. The lips are full, cleancut, under a straight, prominent nose; the large, well-spaced eyes, their expression at once direct and veiled, harbor potential amusement or the quick threat of thunder.
The year 1928 saw him briefly serving with the naval general staff and commanding the light cruiser Isuzu and the carrier Akagi. He was then appointed to the navy ministry's naval affairs bureau, where he was an innovator concerning air safety and navigation. In 1930, Yamamoto served as a special assistant to the Japanese delegation to the London Naval Conference; made rear admiral, he was instrumental in raising the Japanese quota level for light cruisers to 70 percent of American and British forces. From December of 1930 to October of 1933, he headed the technical section of the navy's aviation bureau, and from December of 1935 to December of 1936, he was chief of the bureau itself. Here he directed the entire naval air program—carriers, seaplanes, and land-based craft.
All this time, Yamamoto fought for naval parity with the other great sea powers. For example in 1934, when another naval conference was held in London, Yamamoto—now vice admiral and chief delegate—firmly rejected any further extension of the 5-5-3 ratio. This quota, established at the Washington Conference of 1921-22, had limited Japanese building of heavy warships to 60 percent of American and British construction. Calling the existing ratio a "national degradation," he demanded full equality, using the analogy of a diplomatic dinner party: "I was never told there that being much shorter than the others I ought to eat only three-fifths of the food on my plate. I ate as much as I needed."
During the attempted putsch of February 26, 1936, an effort to topple Japan's parliamentary government in favor of direct military rule, junior officers at the admiralty asked Yamamoto to join the rebels. He immediately ordered them to return to their desks, to which they responded without a murmur.
In December of 1936, Yamamoto was made vice minister of the Japanese navy and hence was firmly placed in Japan's policymaking élite. He accepted the post reluctantly, for he loved air command and hated politics. In office, he did the expected: promoted the development of aircraft carriers. At the same time, he vainly opposed the construction of new battleships, claiming that they could be sunk by torpedo planes. Yamamoto quoted an old Japanese proverb, "The fiercest serpent may be overcome by a swarm of ants," then elaborated: "These [battle]ships are like elaborate religious scrolls which old people hung up in their homes. They are of no proved worth. They are purely a matter of faith—not reality."
While in office, he took several courageous stands. He opposed army desires for an alliance with Germany, fearing that such an agreement would lead to war with the United States and Britain, the world's two strongest naval powers, and possibly the Soviet Union. Moreover, he noted, the Imperial Navy and indeed the entire Japanese economy depended on imports of raw materials from the United States. In 1937, he opposed Japan's invasion of China, telling a friend, "The stupid army has started again." On December 12, 1937, Japanese planes bombed the U.S. gunboat Panay, cruising China's Yangtse River. Three Americans were killed, and 43 were injured. Yamamoto personally apologized to U.S. Ambassador Joseph C. Grew, saying, "The Navy can only hang its head."
Such views made Yamamoto unpopular and like Admiral Yonai Mitsumasa, Japan's navy minister, he became a target for extremist attacks. The atmosphere became so hostile that tanks and machine guns were installed in the Navy Ministry. Supposedly, extreme rightists offered 100,000 yen as reward for his assassination.
On August 30, 1939, two days before Hitler invaded Poland, Yamamoto was appointed commander-in-chief of the combined fleet. Holding the rank of full admiral, he was operational head of Japan's entire navy; it was the highest honor the Japanese fleet could bestow. In addition, Yonai later said, "It was the only way to save his life—send him off to sea."
When on September 27, 1940, Japan signed the Tripartite Pact with Germany and Italy, Yamamoto warned Premier Konoye Fumimaro concerning possible war with the United States:
If I am told to fight regardless of the consequences, I shall run wild for the first six months or a year, but I have utterly no confidence for the second or third year. The Tripartite Pact has been concluded and we cannot help it. Now that the situation has come to this pass, I hope you will endeavor to avoid a Japanese-American war.
That October, he privately described the nature of the next war by saying:
As I see it, naval operations of the future will consist of capturing an island, then building an airfield in as short a time as possible—within a week or so— moving up air units, and using them to gain air and surface control over the next stretch of the ocean. Do you think we have the kind of industrial capacity to do that?
Already Yamamoto was thinking in terms of bold, almost reckless, strikes. During fleet maneuvers in the spring of 1940, in noting the achievements of carrier-based planes, he thought that an attack on the American fleet, stationed at Pearl Harbor, Hawaii, might be possible, and immediately presented his plan to Fukudome Shigeru, chief of staff of the combined fleet. At the end of July of 1941, Yamamoto said to the commander of the submarine fleet: "If we fight both Britain and America we will be defeated… . If war comes, our only chance is to destroy the fleet at Pearl Harbor and send submarines to the west coast of America."
On July 25, 1941, U.S. President Franklin D. Roosevelt froze Japanese assets in retaliation for its occupation of southern Indochina, a move that severed all trade between the two nations. Now Japan's ever-precious supply of oil was cut off, causing it to seek domination of the petroleum-rich Dutch East Indies and to risk war with the United States and Britain. In late September, Yamamoto visited Admiral Nagano Osami, chief of the naval general staff, to dissuade him from pursuing military plans made on September 6 to fight the United States. If war, however, was truly inevitable, Japan—Yamamoto said—should scrap traditional plans centering on lying in wait for the American battle fleet and ambushing it near Japan itself. Rather than allow a U.S. build-up, Japan must make a preemptive strike, crippling the American navy at the outset of the conflict. Such a move could shift the strategic balance in Japan's favor, protect the all-important southern flank in southeast Asia, and hopefully lead to a negotiated peace.
Yamamoto's plan eventually called for a massive air strike involving all six large carriers of the First Air Fleet; they had to approach within 200 miles of Hawaii without being discovered. Writes his biographer John Dean Potter:
The plan was his—and his alone… . He had supervised the smallest detail, perfected it, fought single-handed past the opposition of every senior admiral, offered to lead it personally from the bridge of the leading carrier—and finally threatened to resign if it were not approved.
In October 1941, Nagano gave his reluctant approval. On December 1, Japan's highest decision-making body, the Imperial Conference, decided upon war with the United States, Britain, and the Netherlands. Emperor Hirohito personally issued the orders to Yamamoto: "You must be determined to meet our expectations by exalting our force and authority throughout the world by annihilating the enemy." Aboard his flagship Yamato, stationed in Japan's Inland Sea, Yamamoto gave the coded attack orders to his strike force: "Climb Mount Niitaka," a reference to a peak in Formosa that was the highest point in the Japanese empire.
On December 7, the greatest air operation the world had yet seen took place—Yamamoto's famous strike on Pearl Harbor. In a single blow, 353 planes from six aircraft carriers almost completely destroyed the U.S. Pacific Fleet; 18 American ships were sunk or disabled as were nearly 200 planes; 2,335 servicemen and 68 civilians were killed. Commander Genda Minoru recommended a second strike, seeking to hit two American aircraft carriers and undamaged fuel tanks on Oahu. Admiral Nagumo Chuichi, the task force's leader, refused. A second strike, he reasoned, would be pressing one's luck and furthermore the Japanese carriers were needed for major offensives in Southeast Asia. Nagumo was a torpedo expert and lacked the needed imagination for such an operation; he had only been given carrier command because he was a senior admiral.
Rear Admiral Kuroshima Kameto immediately sought to overrule Nagumo by ordering a search for the American carriers, but Yamamoto replied: "[Nagumo] may have information we do not have. He must fight his own battle. I have complete faith in him." When his operations officer wanted to transfer Nagumo, Yamamoto responded: "How can I? He is an old-fashioned samurai type. If I move him he will commit hari-kiri because he will consider it such a disgrace."
Because of such restraint, Rear Admiral Edwin T. Layton, a leading U.S. staff officer, can write: "Pearl Harbor may have been a disaster, but it was a long way from being the knockout blow that Yamamoto had intended." Furthermore, by sinking so many battleships and thereby forcing the United States to adopt carrier warfare, Yamamoto had inadvertently contributed to American victory.
Yamamoto was always uneasy about his success, ever possessing a curious fatalism. He wrote a friend: "The fact that we have had a small success at Pearl Harbor is nothing…. Personally I do not think it is a good thing to whip up propaganda to encourage the nation. People should think things over and realize how serious the situation is." To win, he warned, "We would have to march into Washington and sign the treaty in the White House."
On February 27-28, 1942, the battle of Java Sea took place. Fought on both sides entirely by cruisers, it was the biggest surface engagement since Jutland. The Japanese defeated a combined force of Dutch, British, and American ships, thereby enabling Japan to seize oil-rich Java. Yamamoto now had sufficient oil to keep his fleet afloat in the foreseeable future.
Yamamoto anticipated that the United States might attempt a carrier raid on Tokyo. Believing that it was his foremost duty to protect the Imperial City, and the emperor in particular, he established a picketboat line extending over a 1,000-mile front some 600 to 700 miles east of Japan. He also ordered naval aircraft to engage in long-range patrols. On April 18, 1942, some 700 miles from Japan, 16 B-25 bombers from the U.S. carrier Hornet headed for Tokyo. Soon Lieutenant Colonel James H. Doolittle was bombing the Japanese capital as well as such neighboring cities as Yokohama, Kawasaki, and Yokosuka. Although the damage was relatively slight, Yamamoto was shocked, regarding it as a mortifying personal defeat. Writes biographer Potter, noting how impulsive the admiral suddenly became: "There can be no doubt however that his normally clear judgment was warped by the Doolittle raid."
From May 4-8, 1942, the world's first major carrier engagement took place in the Coral Sea. Entirely fought by aircraft, it was the first sea battle in history in which no warship of either side ever saw an enemy craft. The Japanese sought to take Port Moresby in New Guinea, thereby cutting off Australia from Allied aid. Tactically, the battle was a Japanese victory, for they had sunk the carrier Lexington and two smaller warships. Yet Japan lost the carrier Shoho, saw severe damage to the carrier Shokaku, and experienced the loss of most of the Zuikaku's planes. The Japanese commander, Vice Admiral Inouye Shigeyoshi, deprived of most of his striking power in aircraft, withdrew. His failure to pursue the damaged Yorktown drew Yamamoto's ire, though Inouye had little choice. Strategically, the Coral Sea marked a U.S. victory because the Japanese abandoned plans to occupy Port Moresby and attack Australia. Furthermore, Yamamoto was served notice that despite U.S. numerical inferiority, the Japanese fleet was not invincible.
Seeking retribution for the Doolittle raid, Yamamoto decided to draw out what was left of the U.S. Pacific Fleet in a decisive battle. The capture of Midway Island, a coral atoll six miles in diameter and a U.S. base just 1,136 miles from Hawaii, would give Japan an advanced outpost for air and submarine patrols. Furthermore, so Yamamoto believed, the strike would draw out the fullest strength of the U.S. Pacific Fleet. He would establish a lethal ambush, one that would destroy the carriers that had escaped him at Pearl Harbor. Once Midway was seized, Hawaii would be invaded, forcing the U.S. to sue for peace. Conversely, Yamamoto believed that if Japan did not soon engage in a decisive sea battle, its defeat was simply a matter of time. In a sense, Midway was his last chance.
Yamamoto assembled the largest fleet in the history of Japanese naval warfare—some 260 ships, among them 11 battleships, 8 carriers, 22 cruisers, 65 destroyers, and 21 submarines. Also involved were some 700 planes and 100,000 naval personnel.
On the surface, Yamamoto's strategy was extremely sophisticated, perhaps too much so. He divided his fleet into widely separated groups. A northern force, including two carriers, would capture Kiska and Attu, islands at the western end of the Aleutians. This strike would not only divert attention from the main target, Midway, it would keep American forces from using the islands as stepping stones to Japan. (He planned to withdraw Japanese forces from the islands before the grueling winter). The bombing of Dutch Harbor would cause even further diversion. An advance force of Japanese submarines, patrolling west of Hawaii, would warn of any U.S. craft in the vicinity, sinking such ships before they could defend Midway. Twenty-four hours after the Aleutian strike, Admiral Nagumo's striking force of four large carriers would hit Midway from the northwest, followed the next day by Vice Admiral Kondo Nobutake's second fleet of two battleships, a small aircraft carrier, half a dozen heavy cruisers, and an invasion convoy. As the main strength of the American fleet lay in Hawaiian or Australian waters (so the Japanese believed), the strike on Midway would be a complete surprise.
Once Midway was captured, the remnants of the U.S. fleet would be forced to attempt its rescue. But by then the Japanese would have the advantage of position as well as at least a 2:1 advantage in carriers and four to five times the number of screening vessels. At that point, Yamamoto himself would lead the combined fleet's main force, a powerful unit of seven battleships that included the two largest in the world then or since: his flagship Yamato and her sister ship, the Musashi. While he would be shutting the jaws of a gigantic trap, the northern force would come from the Aleutians to cut off the U.S. line of retreat. Notes Layton:
His intricate battle choreography also required that his opponents move according to predicted positions; one false step or foreknowledge of the plan could throw the entire operation into disarray.
In the battle, which took place from June 4 to 6, 1942, Yamamoto operated under many disadvantages. Thanks to American cryptographers, the Japanese sailed into a trap. Some Japanese ships had even mentioned their destination by name, and on May 20 a lengthy order of Yamamoto himself was intercepted. By the last week of May, the United States knew the date, place, and time of operation, as well as the composition of the Japanese forces. Yamamoto's submarines were ordered to report on the presence of American carriers, but they arrived on station 25 minutes too late to do so. Yamamoto's operations officer had information pointing to the presence of a powerful U.S. carrier force, but failed to inform Admiral Nagumo. By maintaining radio silence on his flagship, Yamamoto was unable to give instructions when needed. Not a single senior admiral had been fully briefed; all were drawn into combat on the shortest of notice. Nagumo failed to order an immediate attack once he learned of U.S. ships in the vicinity, thereby dooming his force to destruction.
In the ensuing battle, no surface ships sighted each other or exchanged gunfire. The devastating exchanges were carried out entirely by aircraft at long ranges. Three American carriers unexpectedly appeared, the Enterprise, Hornet, and Yorktown—the last ship fresh from hasty repairs. Within ten minutes, they sank three Japanese carriers—Kaga, Akagi, and Soryu— that comprised close to half of Japan's entire carrier tonnage. The remaining Japanese carrier Hiryu successfully sunk the Yorktown, but later in the day it was hit by the Enterprise.
A particularly crucial turning point took place when Nagumo, having learned that his initial air strike did not succeed in critically damaging Midway, decided to use his reserve planes in a second strike. While his carrier crews were in the act of changing from torpedoes to bombs, his force found itself suddenly exposed to the carrier-based planes of the U.S. Pacific Fleet.
Yamamoto himself took no part in the battle until it was too late. He wanted to engage the Americans with his battleships, and in a desperate move sought the daylight bombing of Midway. Yet not being able to bring his scattered groups together on time, he feared further losses and withdrew. Only 307 Americans died compared to 3,500 Japanese. Henceforth, Japan fought on the defensive. Writes military historian Ronald H. Spector: "For the Japanese, Midway was an ill-conceived, sloppily executed operation." One commentator finds it the most decisive battle since Trafalgar, another the Stalingrad of the Pacific.
Even if conquered by Japan, Midway would have been difficult to hold. It would remain an exposed salient (line of defense), subject to frequent bombing. Although the Japanese were able to conquer Kiska and Attu without real opposition, neither island possessed strategic value. The loss of an undamaged Zeke-Zero fighter in a feint on Dutch Harbor enabled the United States to design the sturdier and more powerful F6F Hellcat.
Yamamoto never fully recovered from the shock of this defeat, although he soon commanded air offensive in the Solomons campaign. Noting the strategic importance of Guadalcanal, he realized that the establishment of an American base there challenged his domination of the South Pacific. Engaging in a war of attrition to dislodge U.S. marines who started landing on August 7, 1942, Yamamoto's fleet suffered huge losses of aircraft and pilots. After major efforts, he realized that his destroyer transports, called the "Tokyo Express," could not remove the Americans. Finally, on January 4, 1943, he ordered the evacuation of that island's 13,000 Japanese troops; doing so was one of the great tactical successes of the war. He confessed to an old classmate: "I do not know what to do next."
In an effort to build morale, Yamamoto decided to make inspection trips throughout the South Pacific. In particular, he wanted to thank troops recovering from their ordeal on Guadalcanal. At age 59, he was tired, weary of war, and of life itself: "I have killed quite a few of the enemy, and many of my own men have been killed. So I believe the time has come for me to die too." During the Guadalcanal conflict, his hair had turned snowy-white.
In April 1943, U.S. intelligence intercepted advance reports of Yamamoto's tour. Eighteen American Lightning planes were waiting for the first attempt in history to ambush an enemy commander-in-chief in the air. On the 18th, his aircraft, under the escort of nine zeroes, was shot down by a P-38 near Kahili in southern Bougainville. On June 5, the admiral's ashes were honored in Tokyo in full state ceremony, a tribute accorded only once before—on the exact same day in 1934 to Admiral Togo.
Agawa, Hiroyuli. The Reluctant Admiral: Yamamoto and the Imperial Navy. Translated by John Bester. Kodansha International, 1979.
Hoyt, Edwin B. Yamamoto: The Man Who Planned Pearl Harbor. McGraw-Hill, 1990.
Potter, John Dean. Yamamoto: The Man Who Menaced America. Viking, 1965.
Evans, David C., ed. and trans. The Japanese Navy in World War II: In the Words of Former Naval Officers. Naval Institute Press, 1986.
Prange, Gordon W., Donald M. Goldstein, and Katherine V. Dillon. At Dawn We Slept: The Untold Secret of Pearl Harbor. McGraw-Hill, 1981.
—. Miracle at Midway. McGraw-Hill, 1982.
Spector, Ronald H. Eagle Against the Sun: The American War with Japan. Free Press, 1985.
Toland, John. The Rising Sun: The Decline and Fall of the Japanese Empire, 1936-1945. Random House, 1970. □
"Isoroku Yamamoto." Encyclopedia of World Biography. . Encyclopedia.com. (September 13, 2019). https://www.encyclopedia.com/history/encyclopedias-almanacs-transcripts-and-maps/isoroku-yamamoto
"Isoroku Yamamoto." Encyclopedia of World Biography. . Retrieved September 13, 2019 from Encyclopedia.com: https://www.encyclopedia.com/history/encyclopedias-almanacs-transcripts-and-maps/isoroku-yamamoto
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The orthodox strategy of the Japanese naval General Staff was to wait for the U.S. Fleet to steam into the western Pacific and destroy it there in a battleship contest. To Yamamoto, a pioneer of naval aviation and a long‐standing lover of games of chance, this was a weak‐hearted approach. He insisted on a preemptive carrier strike on Pearl Harbor to destroy the U.S. Fleet at the outset. The navy staff opposed him, and only his immense moral stature allowed him to prevail.
The attack on 7 December 1941 proved a brilliant tactical success, and strategically it achieved its objective of protecting Japan's Southeast Asian offensives. But the wave of American public anger that it aroused made impossible a limited settlement of the war. Yamamoto continued to command the fleet in 1942 and 1943, but less successfully. The disastrous Japanese defeat at the Battle of Midway was his responsibility, and his air offensives in the Solomons wore down Japanese naval airpower relentlessly. On 18 April 1943, Yamamoto was on his way to visit forward units in the Solomon Islands when his plane was shot down by U.S. P‐38s, alerted to his route by reading the Japanese naval codes.
[See also MAGIC; World War II, U.S. Naval Operations in: The Pacific.]
Hiroyuki Agawa , The Reluctant Admiral. Yamamoto and the Imperial Navy, 1979.
Shinjimbutsu Oraisha , Yamamoto Isoroku no subete, 1985.
David C. Evans
"Yamamoto, Isoroku." The Oxford Companion to American Military History. . Encyclopedia.com. (September 13, 2019). https://www.encyclopedia.com/history/encyclopedias-almanacs-transcripts-and-maps/yamamoto-isoroku
"Yamamoto, Isoroku." The Oxford Companion to American Military History. . Retrieved September 13, 2019 from Encyclopedia.com: https://www.encyclopedia.com/history/encyclopedias-almanacs-transcripts-and-maps/yamamoto-isoroku
Modern Language Association
The Chicago Manual of Style
American Psychological Association
Isoroku Yamamoto (ēsō´rōkōō´ yämä´mōtō), 1884–1943, Japanese admiral in World War II. He headed the combined fleet in 1941 and was the mastermind behind Japan's attack on Pearl Harbor. After he was killed in action in 1943, he became a national hero. Throughout his career he worked to build an integrated air-surface arm for the navy.
See H. Hagawa, The Reluctant Admiral (1982).
"Yamamoto, Isoroku." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (September 13, 2019). https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/yamamoto-isoroku
"Yamamoto, Isoroku." The Columbia Encyclopedia, 6th ed.. . Retrieved September 13, 2019 from Encyclopedia.com: https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/yamamoto-isoroku