Isoroku Yamamoto

Isoroku Yamamoto (山本 五十六) was a Japanese Marshal Admiral and the commander-in-chief of the Combined Fleet during World War II, a graduate of the Imperial Japanese Naval Academy.

Yamamoto held several important posts in the Imperial Japanese Navy, and undertook many of its changes and reorganizations, especially its development of naval aviation. He was the commander-in-chief during the decisive early years of the Pacific War and so was responsible for major battles such as Pearl Harbor and Midway. He died when American codebreakers identified his flight plans and his plane was shot down. His death was a major blow to Japanese military morale during World War II.

Family background
Yamamoto was born Isoroku Takano (高野 五十六) in Nagaoka, Niigata. His father was Takano Sadayoshi (高野 貞吉), an intermediate-rank samurai of the Nagaoka Domain. "Isoroku" is an old Japanese term meaning "56"; the name referred to his father's age at Isoroku's birth.

In 1916, Isoroku was adopted into the Yamamoto family (another family of former Nagaoka samurai) and took the Yamamoto name. It was a common practice for Japanese families lacking sons to adopt suitable young men in this fashion to carry on the family name, the rank and the income that comes with it. In 1918 Isoroku married Reiko Mihashi, with whom he had two sons and two daughters.

Early career
After graduating from the Imperial Japanese Naval Academy in 1904, Yamamoto served on the armored cruiser JAPANESE CRUISER Nisshin during the Russo-Japanese War. He was wounded at the Battle of Tsushima, losing two fingers (the index and middle fingers) on his left hand, as the cruiser was hit repeatedly by the Russian battleline. He returned to the Naval Staff College in 1914, emerging as a Lieutenant Commander in 1916.

1920s and 1930s
Yamamoto was part of the Japanese Navy establishment, who were rivals of the more aggressive Army establishment, especially the officers of the Kwantung Army. As such he promoted a policy of a strong fleet to project force through gunboat diplomacy, rather than a fleet used primarily for transport of invasion land forces, as some of his political opponents in the army wanted. This stance led him to oppose the invasion of China. He also opposed war against the United States partly because of his studies at Harvard University (1919–1921) and his two postings as a naval attaché in Washington, D.C. He learned to speak fluent English as a result. Yamamoto traveled extensively in the United States during his tour of duty there, where he studied American customs and business practices. He showed a keen interest in the American petroleum industry, and became so well-versed with its workings that he received job offers from American oilmen.

He was promoted to Captain in 1923. On 13 April 1924 at the rank of captain, he was part of the Japanese delegation visiting the U.S. Naval War College. Later that year, he changed his specialty from gunnery to naval aviation. His first command was the cruiser JAPANESE CRUISER Isuzu in 1928, followed by the aircraft carrier JAPANESE AIRCRAFT CARRIER Akagi.

He participated in the second London Naval Conference of 1930 as a Rear Admiral and the 1934 London Naval Conference as a Vice Admiral, as the government felt that a career military specialist needed to accompany the diplomats to the arms limitations talks. Yamamoto was a strong proponent of naval aviation, and served as head of the Aeronautics Department before accepting a post as commander of the First Carrier Division. Yamamoto personally opposed the invasion of Manchuria in 1931, the subsequent land war with China (1937), and the 1940 Tripartite Pact with Nazi Germany and Fascist Italy. As Deputy Navy Minister, he apologized to United States Ambassador Joseph C. Grew for the bombing of the gunboat USS Panay (PR-5) in December 1937. These issues made him a target of assassination threats by pro-war militarists.

Throughout 1938, many young army and naval officers began to speak publicly against Yamamoto and certain other Japanese admirals such as Mitsumasa Yonai and Shigeyoshi Inoue for their strong opposition towards a Tripartite pact with Nazi Germany for reportedly being against "Japan's natural interests." Yamamoto himself received a steady stream of hate mail and death threats from Japanese nationalists but his reaction to the prospect of death by assassination was passive and accepting. The Admiral wrote: "To die for Emperor and Nation is the highest hope of a military man. After a brave hard fight the blossoms are scattered on the fighting field. But if a person wants to take a life instead, still the fighting man will go to eternity for Emperor and country. One man's life or death is a matter of no importance. All that matters is the Empire. As Confucius said, "They may crush cinnabar, yet they do not take away its color; one may burn a fragrant herb, yet it will not destroy the scent." They may destroy my body, yet they will not take away my will."

The Japanese army, annoyed at Yamamoto's unflinching opposition to a Rome-Berlin-Tokyo treaty, dispatched military police to "guard" Yamamoto; this was an attempt by the Army to keep an eye on him. He was later reassigned from the Navy Ministry to sea as the Commander-in-Chief of the Combined Fleet on (30 August 1939). This was done as one of the last acts of the then-acting Navy Minister Mitsumasa Yonai, under Baron Hiranuma's short-lived administration partly to make it harder for assassins to target Yamamoto; Yonai was certain that if Yamamoto remained ashore, he would be killed before the year (1939) ended.

1940–1941
Yamamoto was promoted to Naval General (Admiral) on 15 November 1940. This, in spite of the fact that when Hideki Tōjō was appointed Prime Minister on 18 October 1941, many political observers thought that Yamamoto's career was essentially over. Tōjō had been Yamamoto's old opponent from the time when the latter served as Japan's deputy navy minister and Tōjō was the prime mover behind Japan's takeover of Manchuria. It was believed that Yamamoto would be appointed to command the Yokosuka Naval Base, "a nice safe demotion with a big house and no power at all." After the new Japanese cabinet was announced, however, Yamamoto found himself left alone in his position despite his open conflicts with Tōjō and other members of the army's oligarchy who favored war with the European powers and America. Two of the main reasons for Yamamoto's political survival were his immense popularity within the fleet, where he commanded the respect of his men and officers, and his close relations with the imperial family. He also had the acceptance by Japan's naval hierarchy: ""[T]here was no officer more competent to lead the Combined Fleet to victory than Admiral Yamamoto. His daring plan for the Pearl Harbor attack had passed through the crucible of the Japanese naval establishment, and after many expressed misgivings, his fellow admirals had realized that Yamamoto spoke no more than the truth when he said that Japan's hope for victory in this [upcoming] war was limited by time and oil. Every sensible officer of the navy was well aware of the perennial oil problems. Also, it had to be recognized that if the enemy could seriously disturb Japanese merchant shipping, then the fleet would be endangered even more.""

Consequently, Yamamoto stayed in his post. With Tōjō now in charge of Japan's highest political office, it became clear the army would lead the navy into a war about which Yamamoto had serious reservations. He wrote to an ultranationalist:

"Should hostilities once break out between Japan and the United States, it would not be enough that we take Guam and the Philippines, nor even Hawaii and San Francisco. To make victory certain, we would have to march into Washington and dictate the terms of peace in the White House. I wonder if our politicians (who speak so lightly of a Japanese-American war) have confidence as to the final outcome and are prepared to make the necessary sacrifices."

This quote was spread by the militarists, minus the last sentence, where it was interpreted in America as a boast that Japan would conquer the entire continental United States. The omitted sentence showed Yamamoto's counsel of caution towards a war that could cost Japan dearly. Nevertheless, Yamamoto accepted the reality of impending war and planned for a quick victory by destroying the US fleet at Pearl Harbor in a preventive strike while simultaneously thrusting into the oil and rubber resource rich areas of Southeast Asia, especially the Dutch East Indies, Borneo and Malaya. In naval matters, Yamamoto opposed the building of the super-battleships JAPANESE BATTLESHIP Yamato and JAPANESE BATTLESHIP Musashi as an unwise investment of resources.

Yamamoto was responsible for a number of innovations in Japanese naval aviation. Although remembered for his association with aircraft carriers due to Pearl Harbor and Midway, Yamamoto did more to influence the development of land-based naval aviation, particularly the Mitsubishi G3M and G4M medium bombers. His demand for great range and the ability to carry a torpedo was intended to conform to Japanese conceptions of attriting the American fleet as it advanced across the Pacific in war. The planes did achieve long range, but long-range fighter escorts were not available. These planes were lightly constructed and when fully fueled, they were especially vulnerable to enemy fire. This earned the G4M the sardonic nickname "the Flying Cigarette Lighter." Yamamoto would eventually die in one of these aircraft.

The range of the G3M and G4M contributed to a demand for great range in a fighter aircraft. This partly drove the requirements for the A6M Zero which was as noteworthy for its range as for its maneuverability. Both qualities were again purchased at the expense of light construction and flammability that later contributed to the A6M's high casualty rates as the war progressed.



As Japan moved toward war during 1940, Yamamoto gradually moved toward strategic as well as tactical innovation, again with mixed results. Prompted by talented young officers such as Lieutenant Commander Minoru Genda, Yamamoto approved the reorganization of Japanese carrier forces into the First Air Fleet, a consolidated striking force that gathered Japan's six largest carriers into one unit. This innovation gave great striking capacity, but also concentrated the vulnerable carriers into a compact target; both boon and bane would be realized in war. Yamamoto also oversaw the organization of a similar large land-based organization in the 11th Air Fleet, which would later use the G3M and G4M to neutralize American air forces in the Philippines and sink the British Force "Z".

In January 1941, Yamamoto went even further and proposed a radical revision of Japanese naval strategy. For two decades, in keeping with the doctrine of Captain Alfred T. Mahan, the Naval General Staff had planned in terms of Japanese light surface forces, submarines and land-based air units whittling down the American Fleet as it advanced across the Pacific until the Japanese Navy engaged it in a climactic "Decisive Battle" in the northern Philippine Sea (between the Ryukyu Islands and the Marianas Islands), with battleships meeting in the traditional exchange between battle lines.

Correctly pointing out this plan had never worked even in Japanese war games, and painfully aware of American strategic advantages in military productive capacity, Yamamoto proposed instead to seek a decision with the Americans by first reducing their forces with a preventive strike, and following it with a "Decisive Battle" fought offensively, rather than defensively. Yamamoto hoped, but probably did not believe, if the Americans could be dealt such terrific blows early in the war, they might be willing to negotiate an end to the conflict. As it turned out, however, the note officially breaking diplomatic relations with the United States was delivered late, and he correctly perceived the Americans would be resolved upon revenge and unwilling to negotiate. At the end of the attack upon Pearl Harbor, upon hearing of the mis-timing of the communique breaking diplomatic relations with the United States earlier that day, it is reputed Yamamoto said, "I fear all we have done today is to awaken a great, sleeping giant."; however, there is no documented evidence the statement was made.

The Naval General Staff proved reluctant to go along and Yamamoto was eventually driven to capitalize on his popularity in the fleet by threatening to resign to get his way. Admiral Osami Nagano and the Naval General Staff eventually caved in to this pressure, but only insofar as approving the attack on Pearl Harbor.

The First Air Fleet commenced preparations for the Pearl Harbor Raid, solving a number of technical problems along the way, including how to launch torpedoes in the shallow water of Pearl Harbor and how to craft armor-piercing bombs by machining down battleship gun projectiles.

Attack on Pearl Harbor
As Yamamoto had planned, the First Air Fleet of six carriers commenced hostilities against the Americans on 7 December 1941, launching 353 aircraft against Pearl Harbor in two waves. The attack was a complete success according to the parameters of the mission which sought to sink at least four American battleships and prevent the U.S. Fleet from interfering in Japan's southward advance for at least six months. American aircraft carriers were also considered a choice target, but these were not in port at the time of the attack.



In the end, five American battleships were sunk, three were damaged, and eleven other cruisers, destroyers and auxiliaries were sunk or seriously damaged. The Japanese lost only 29 aircraft, while 74 were damaged from anti-aircraft fire from the ground. The damaged aircraft were disproportionately dive and torpedo bombers, seriously impacting available firepower to exploit the first two waves' success, so the commander of the First Air Fleet, Naval Lieutenant-General Chuichi Nagumo, withdrew. Yamamoto later lamented Nagumo's failure to seize the initiative to seek out and destroy the American carriers, absent from the harbor, or further bombard various strategically important facilities on Oahu. Nagumo had absolutely no idea where the American carriers might be, and remaining on station while his forces cast about looking for them ran the risk of his own forces being found first and attacked while his aircraft were absent searching. In any case, insufficient daylight remained after recovering the aircraft from the first two waves for the carriers to launch and recover a third before dark, and Nagumo's escorting destroyers lacked the fuel capacity for him to loiter long. Much has been made of Yamamoto's hindsight, but (in keeping with Japanese military tradition not to criticize the commander on the spot), he did not punish Nagumo in any way for his withdrawal.

On the strategic level, the attack was a disaster for Japan, rousing American passions for revenge due to it being a "sneak attack". The shock of the attack coming in an unexpected place, with such devastating results and without the expected "fair play" of a declaration of war galvanized the American public's determination to avenge the attack. When asked by Prime Minister Fumimaro Konoe in mid-1941 concerning the outcome of a possible war with the United States, Yamamoto made a well-known and prophetic statement: If ordered to fight, "I shall run wild considerably for the first six months or a year, but I have utterly no confidence for the second and third years." His prediction would be vindicated as Japan easily conquered territories and islands for the first six months of the war until it suffered a shattering defeat at the Battle of Midway on 4–7 June 1942, which ultimately tilted the balance of power in the Pacific towards the U.S.

As a strategic blow intended to prevent American interference in the Dutch East Indies for six months, the Pearl Harbor attack was a success, but unbeknownst to Yamamoto, it was a pointless one. The U.S. Navy had abandoned any intention of attempting to charge across the Pacific towards the Philippines at the outset of war in 1935 (in keeping with the evolution of War Plan Orange). In 1937, the U.S. Navy had further determined even fully manning the fleet to wartime levels could not be accomplished in less than six months, and myriad other logistic assets needed to execute a trans-Pacific movement simply did not exist and would require two years to construct after the onset of war. In 1940, U.S. Chief of Naval Operations, Admiral Harold Stark had penned "Plan Dog", which emphasized a defensive war in the Pacific while the U.S. concentrated on defeating Nazi Germany first, and consigned Admiral Husband Kimmel's Pacific Fleet to merely keeping the Imperial Japanese Navy (IJN) out of the eastern Pacific and away from the shipping lanes to Australia. Moreover, it is in question whether the U.S. would have gone to war at all had Japan only attacked British and Dutch possessions in the Far East.

December 1941 to May 1942
With the American Fleet largely neutralized at Pearl Harbor, Yamamoto's Combined Fleet turned to the task of executing the larger Japanese war plan devised by the Imperial Japanese Army and Navy General Staff. The First Air Fleet proceeded to make a circuit of the Pacific, striking American, Australian, Dutch and British installations from Wake Island to Australia to Ceylon in the Indian Ocean. The 11th Air Fleet caught the American 5th Air Force on the ground in the Philippines hours after Pearl Harbor, and then proceeded to sink the British Force "Z" (battleship HMS Prince of Wales (53) and battlecruiser HMS Repulse (1916)) underway at sea.

Under Yamamoto's able subordinates, Naval Lieutenant-Generals Jisaburō Ozawa, Nobutake Kondō and Ibō Takahashi, the Japanese swept the inadequate remaining American, British, Dutch and Australian naval assets from the Dutch East Indies in a series of amphibious landings and surface naval battles that culminated in the Battle of the Java Sea on 27 February 1942. With the occupation of the Dutch East Indies, and the reduction of the remaining American positions in the Philippines on the Bataan Peninsula and Corregidor island, the Japanese had secured their oil- and rubber-rich "Southern Resources Area".

By late March, having achieved their initial aims with surprising speed and little loss (albeit against enemies ill-prepared to resist them), the Japanese paused to consider their next moves. Yamamoto and a few Japanese military leaders and officials waited, hoping that the United States or Great Britain would negotiate for an armistice or a peace treaty to end the war in their favour. But when the British, as well as the Americans, expressed no interest in negotiating with Japan for any cease fire, the Japanese thoughts turned to securing and protecting their newly seized territory, and acquiring more with an eye toward additional conquest and/or attempting to force one or more of their enemies out of the war.

Competing plans were developed at this stage, including thrusts to the west against India, the south against Australia and the east against the United States. Yamamoto was involved in this debate, supporting different plans at different times with varying degrees of enthusiasm and for varying purposes, including "horse-trading" for support of his own objectives.

Plans included ideas as ambitious as invading India or Australia, or seizing Hawaii. These grandiose ventures were inevitably set aside as the army could not spare enough troops from China for the first two (which would require a minimum of 250,000 men), nor shipping to support the latter two. (Shipping was allocated separately to IJN & IJA, and jealously guarded. ) Instead, the Imperial General Staff supported an army thrust into Burma in hopes of linking up with Indian Nationalists revolting against British rule, and attacks in New Guinea and the Solomon Islands designed to imperil Australia's sea line of communication with the United States. Yamamoto agitated for an offensive decisive battle in the east to finish off the American fleet, but the more conservative Naval General Staff officers were unwilling to risk it.

On 18 April, in the midst of these debates, the Doolittle Raid struck Tokyo and the surrounding areas, galvanizing the threat posed by the American aircraft carriers in the minds of staff officers, and giving Yamamoto an event he could exploit to get his way as further debate over military strategy came to a quick end. The Naval General Staff agreed to Yamamoto's Midway (MI) Operation, subsequent to the first phase of the operations against Australia's link with America, and concurrent with their own plan to seize positions in the Aleutian Islands.

Yamamoto rushed planning for the Midway and Aleutians missions, while dispatching a force under Naval Major-General Takeo Takagi, including the Fifth Carrier Division (the large, new carriers JAPANESE AIRCRAFT CARRIER Shōkaku and JAPANESE AIRCRAFT CARRIER Zuikaku), to support the effort to seize the islands of Tulagi and Guadalcanal for seaplane and aeroplane bases, and the town of Port Moresby on Papua New Guinea's south coast facing Australia.

The Port Moresby (MO) Operation proved an unwelcome setback. Although Tulagi and Guadalcanal were taken, the Port Moresby invasion fleet was compelled to turn back when Takagi clashed with an American carrier task force in the Battle of the Coral Sea in early May. Although the Japanese sank the American carrier USS Lexington (CV-2) and damaged the USS Yorktown (CV-5), the Americans damaged the carrier Shōkaku so badly that she required dockyard repairs, and the Japanese lost the light carrier JAPANESE AIRCRAFT CARRIER Shoho. Just as importantly, Japanese operational mishaps and American fighters and anti-aircraft fire devastated the dive bomber and torpedo plane formations of both Shōkakus and Zuikakus air groups. These losses sidelined Zuikaku while she awaited replacement aircraft and aircrews, and saw to tactical integration and training. These two ships would be sorely missed a month later at Midway.

Battle of Midway, June 1942
Yamamoto's plan for Midway Island was an extension of his efforts to knock the U.S. Pacific Fleet out of action long enough for Japan to fortify her defensive perimeter in the Pacific island chains. Yamamoto felt it necessary to seek an early, offensive decisive battle.

This plan was long believed to have been to draw American attention—and possibly carrier forces—north from Pearl Harbor by sending his Fifth Fleet (two light carriers, five cruisers, 13 destroyers, and four transports) against the Aleutians, raiding Dutch Harbor on Unalaska Island and invading the more distant islands of Kiska and Attu. Recent scholarship using Japanese language documents has revealed it was, rather, an unrelated venture of the Naval General Staff which Yamamoto agreed to conduct concurrently with the Midway operation, in exchange for the latter's approval.

While Fifth Fleet attacked the Aleutians, First Mobile Force (4 carriers, 2 battleships, 3 cruisers, and 12 destroyers) would raid Midway and destroy its air force. Once this was neutralized, Second Fleet (1 light carrier, 2 battleships, 10 cruisers, 21 destroyers, and 11 transports) would land 5,000 troops to seize the atoll from the American Marines.

The seizure of Midway was expected to draw the American carriers west into a trap where the First Mobile Force would engage and destroy them. Afterward, First Fleet (1 light carrier, 7 battleships, 3 cruisers and 13 destroyers), in conjunction with elements of Second Fleet, would mop up remaining American surface forces and complete the destruction of the Pacific Fleet.

To guard against mischance, Yamamoto initiated two security measures. The first was an aerial reconnaissance mission (Operation K) over Pearl Harbor to ascertain if the American carriers were there. The second was a picket line of submarines to detect the movement of the American carriers toward Midway in time for First Mobile Force, First Fleet, and Second Fleet to combine against it. In the event, the first was aborted and the second delayed until after American carriers had sortied.

The plan was a compromise and hastily prepared (apparently so it could be launched in time for the anniversary of Tsushima), but appeared well thought out, well organized, and finely timed when viewed from a Japanese viewpoint. Against four carriers, two light carriers, 11 battleships, 16 cruisers and 46 destroyers likely to be in the area of the main battle the Americans could field only three carriers, eight cruisers, and 15 destroyers. The disparity appeared crushing. Only in numbers of carrier decks, available aircraft, and submarines was there near parity between the two sides. Despite various frictions developed in the execution, it appeared — barring something extraordinary — Yamamoto held all the cards.

Unfortunately for Yamamoto, something extraordinary had happened. The worst fear of any commander is for an enemy to learn his battle plan in advance, which was exactly what American cryptographers had done, thanks to breaking the Japanese naval code D (known to the U.S. as JN-25). As a result, Admiral Chester Nimitz, the Pacific Fleet commander, was able to circumvent both of Yamamoto's security measures and position his outnumbered forces in the exact position to conduct a devastating ambush. By Nimitz's calculation, his three available carrier decks, plus Midway, gave him rough parity with Nagumo's First Mobile Force.

Following a nuisance raid by Japanese flying boats in May, Nimitz dispatched a minesweeper to guard the intended refueling point for Operation K near French Frigate Shoals, causing the reconnaissance mission to be aborted and leaving Yamamoto ignorant of whether Pacific Fleet carriers were still at Pearl Harbor. (It remains unclear why Yamamoto permitted the earlier attack, and why his submarines did not sortie sooner, as reconnaissance was essential to the success of MI.) He also dispatched his carriers toward Midway early, and they passed the intended picket line force of submarines en route to their station, negating Yamamoto's back-up security measure. Nimitz's carriers positioned themselves to ambush the Kido Butai (Striking Force) when it struck Midway. A token cruiser and destroyer force was sent toward the Aleutians, but otherwise Nimitz ignored them. On 4 June 1942, days before Yamamoto expected them to interfere in the Midway operation, American carrier-based aircraft destroyed the four carriers of the Kido Butai, catching the Japanese carriers at an especially vulnerable moment.

With his air power destroyed and his forces not yet concentrated for a fleet battle, Yamamoto attempted to maneuver his remaining forces, still strong on paper, to trap the American forces. He was unable to do so because his initial dispositions had placed his surface combatants too far from Midway, and because Admiral Raymond Spruance prudently withdrew to the east in a position to further defend Midway Island, believing (based on a mistaken submarine report) the Japanese still intended to invade. Not knowing several battleships, including the powerful JAPANESE BATTLESHIP Yamato, were on the Japanese order of battle, he did not comprehend the severe risk of a night surface battle, in which his carriers and cruisers would be at a disadvantage. However, his move to the east did avoid the possibility of such a battle taking place. Correctly perceiving he had lost and could not bring surface forces into action, Yamamoto aborted the invasion of Midway and withdrew. The defeat marked the high tide of Japanese expansion.

Yamamoto's plan for MI has been the subject of much criticism. Many commentators state it violated the principle of concentration of force, and was overly complex. Others point out similarly complex Allied operations (such as Operation MB8) that were successful, and note the extent to which the American intelligence coup derailed the operation before it began. Had Yamamoto's dispositions not denied Nagumo adequate pre-attack reconnaissance assets, both the American cryptanalytic success and the unexpected appearance of Fletcher's carriers would have been irrelevant.

Actions after Midway
The Battle of Midway solidly checked Japanese momentum, but the IJN was still a powerful force and capable of regaining the initiative. They planned to resume the thrust with Operation FS aimed at eventually taking Samoa and Fiji to cut the American life-line to Australia. This was expected to short-circuit the threat posed by General Douglas MacArthur and his American and Australian forces in New Guinea. To this end, development of the airfield on Guadalcanal continued and attracted the baleful eye of Yamamoto's opposite number, Admiral Ernest King.

To prevent the Japanese from regaining the initiative, King ramrodded the idea of an immediate American counterattack through the Joint Chiefs of Staff. This precipitated the American invasion of Guadalcanal and beat the Japanese to the punch, with Marines landing on the island in August 1942 and starting a bitter struggle that lasted until February 1943 and commenced a battle of attrition Japan could ill afford.

Yamamoto remained in command as Commander-in-Chief, retained at least partly to avoid diminishing the morale of the Combined Fleet. However, he had lost face in the Midway defeat and the Naval General Staff were disinclined to indulge further gambles. This reduced Yamamoto to pursuing the classic defensive Decisive Battle strategy he had attempted to overturn.

The naval and land battles at Guadalcanal caught the Japanese over-extended and attempting to support fighting in New Guinea while guarding the Central Pacific and preparing to conduct Operation FS. The FS operation was abandoned and the Japanese attempted to fight in both New Guinea and Guadalcanal at the same time. Already stretched thin, they suffered repeated setbacks due to a lack of shipping, a lack of troops, and a disastrous inability to coordinate Army and Navy activities.

Yamamoto committed Combined Fleet units to a series of small attrition actions across the south and central Pacific that stung the Americans, but suffered losses he could ill afford in return. Three major efforts to carry the island precipitated a pair of carrier battles that Yamamoto commanded personally at the Eastern Solomons and Santa Cruz Islands in September and October, and finally a wild pair of surface engagements in November, all timed to coincide with Japanese Army pushes. The timing of each major battle was successively derailed when the army could not hold up its end of the operation. Yamamoto's naval forces won a few victories and inflicted considerable losses and damage to the U.S. Fleet in several naval battles around Guadalcanal which included the battles of Savo Island, Cape Esperance, and Tassafaronga, but he could never draw the Americans into a decisive fleet action. As a result, the Japanese Navy's strength began to bleed off.

There were severe losses of carrier dive-bomber and torpedo-bomber crews in the carrier battles, emasculating the already depleted carrier air groups. Japan could not hope to match the United States in quantities of well-trained replacement pilots, and the quality of both Japanese land-based and naval aviation began declining. Particularly harmful, however, were losses of numerous destroyers in the unsuccessful Tokyo Express supply runs. The IJN already faced a shortage of such ships, and these losses further exacerbated Japan's already weakened commerce defense. With Guadalcanal lost in February 1943, there was no further attempt to seek a major battle in the Solomon Islands although smaller attrition battles continued. Yamamoto shifted the load of the air battle away from the depleted carriers and to the land-based naval air forces.

Death
To boost morale following the defeat at Guadalcanal, Yamamoto decided to make an inspection tour throughout the South Pacific. On 14 April 1943, the US naval intelligence effort, code-named "Magic", intercepted and decrypted a message containing specific details regarding Yamamoto's tour, including arrival and departure times and locations, as well as the number and types of planes that would transport and accompany him on the journey. Yamamoto, the itinerary revealed, would be flying from Rabaul to Balalae Airfield, on an island near Bougainville in the Solomon Islands, on the morning of 18 April 1943.

U.S. President Franklin D. Roosevelt ordered Secretary of the Navy Frank Knox to "Get Yamamoto." Knox instructed Admiral Chester W. Nimitz of Roosevelt's wishes. Admiral Nimitz consulted Admiral William F. Halsey, Jr., Commander, South Pacific, then authorized a mission on 17 April to intercept Yamamoto's flight en route and shoot it down. A squadron of Lockheed P-38 Lightning aircraft were assigned the task as only they possessed the range to intercept and engage. Select pilots from three units were informed that they were intercepting an "important high officer" with no specific name given.

On the morning of 18 April, despite urgings by local commanders to cancel the trip for fear of ambush, Yamamoto's two Mitsubishi G4M fast transport aircraft left Rabaul as scheduled for the 315 mi trip. Sixteen Lightnings intercepted the flight over Bougainville and a dogfight ensued between them and the six escorting Mitsubishi A6M Zeroes. First Lieutenant Rex T. Barber engaged the first of the two Japanese transports which turned out to be Yamamoto's plane. He targeted the aircraft with gunfire until it began to spew smoke from its left engine. Barber turned away to attack the other transport as Yamamoto's plane crashed into the jungle.

The crash site and body of Yamamoto were found the next day in the jungle north of Buin by a Japanese search and rescue party, led by army engineer, Lieutenant Hamasuna. According to Hamasuna, Yamamoto had been thrown clear of the plane's wreckage, his white-gloved hand grasping the hilt of his katana, still upright in his seat under a tree. Hamasuna said Yamamoto was instantly recognizable, head dipped down as if deep in thought. A post-mortem of the body disclosed that Yamamoto had received two 50-caliber bullet wounds, one to the back of his left shoulder and another to his left lower jaw that exited above his right eye. The Japanese navy doctor examining the body determined that the head wound killed Yamamoto. The more violent details of Yamamoto's death were hidden from the Japanese public; the medical report was whitewashed, changed "on orders from above", according to biographer Hiroyuki Agawa.

His staff cremated his remains at Buin, and the ashes were returned to Tokyo aboard the battleship JAPANESE BATTLESHIP Musashi, Yamamoto's last flagship. Yamamoto was given a full state funeral on 5 June 1943, where he received, posthumously, the title of Marshal and was awarded the Order of the Chrysanthemum, (1st Class). He was also awarded Nazi Germany's Knight's Cross of the Iron Cross with Oak Leaves and Swords. Part of his ashes were buried in the public Tama Cemetery, Tokyo (多摩霊園), and the remainder at his ancestral burial grounds at the temple of Chuko-ji in Nagaoka City. He was succeeded as commander-in-chief of the Combined Fleet by Admiral Mineichi Koga.

Personal life
While other military leaders avoided the image of being "soft", Yamamoto continued to practice calligraphy. He and his wife, Reiko, had four children: two sons and two daughters. Yamamoto was an avid gambler, enjoying shogi, billiards, bridge, mah jong, poker, and other games that tested his wits and sharpened his mind. He frequently made jokes about moving to Monaco and starting his own casino. He enjoyed the company of geisha, and his wife Reiko revealed to the Japanese public in 1954 that Yamamoto was closer to his favorite geisha Kawai Chiyoko than to her, which stirred some controversy. After his death, his funeral procession passed by Kawai's quarters on the way to the cemetery, perhaps with a hidden purpose.

Yamamoto as a commander
Yamamoto is generally regarded as one of the most prominent leaders in the IJN for making significant changes to its organization, although he was also responsible for several critical defeats. Yamamoto is considered to be an imaginative and brave leader for formulating a plan to launch a preventive attack on US forces in the Pacific Fleet. Allied Naval leaders such as Nimitz and Halsey respected his abilities and considered him a highly capable and resourceful adversary. He is known as one of the very few military leaders who vocally opposed the occupation of China, the Tripartite Pact, and the war with the U.S., though in doing so he received death threats from nationalists.

Having studied at Harvard University, he was reluctant to enter into war with the United States. He was aware of their overwhelming industrial capacity compared to that of Japan, and felt that only a knockout blow would remove the US threat to Japan. He also did not trust Nazi Germany; somewhat ironically, he became the only non-German to be given the Knight's Cross with Oak Leaves and Swords, which was awarded posthumously. He correctly anticipated that the aircraft carrier would play a role in any decisive battle with the United States. Furthermore, he supported increasing the striking power of the air fleets by combining all six of Japan's large aircraft carriers into one carrier battle group. Additionally, he often assigned capable individuals such as Minoru Genda to form his battle plans.

His forces suffered severely in certain areas, with Allied submarines dealing major blows to the Imperial Japanese Navy shipping and causing the war economy of Japan to be starved of resources, although the full weight of the blow began to be truly felt only in 1943, when American codebreakers cracked the merchant marine code again, and 1944, after technical deficiencies in the Mark 14 torpedo were finally resolved. The Imperial Japanese Navy's codes were decrypted by the United States; this proved to be a fatal development, as it resulted in the biggest direct blow to the Imperial Japanese Navy at the Battle of Midway. The battle proved to be Yamamoto's most prominent defeat, with the Japanese navy losing four of its six fleet carriers and 248 aircraft, with over 3000 men dead; losses which Japan could never replace.

Yamamoto's career promotions

 * Midshipman—14 November 1904
 * Ensign—31 August 1905
 * Sublieutenant—28 September 1907
 * Lieutenant—11 October 1909
 * Lieutenant Commander—13 December 1915
 * Commander—1 December 1919
 * Captain—1 December 1923
 * Rear Admiral—30 November 1929
 * Vice Admiral—15 November 1934
 * Admiral—15 November 1940
 * Marshal-Admiral—18 April 1943 (posthumous)

Media portrayals
Since the end of the Second World War, a number of Japanese and American films have depicted the character of Isoroku Yamamoto.

One of the most notable films is the 1970 movie Tora! Tora! Tora!, which stars Japanese actor Sô Yamamura as Yamamoto, who states after the attack on Pearl Harbor: "I fear that all we have done is to awaken a sleeping giant and fill him with a terrible resolve." There is no evidence that Yamamoto said this in reality despite the film calling it a quote. (See Isoroku Yamamoto's sleeping giant quote for further discussion.)

The first film to feature Yamamoto was Toho's 1953 film Taiheiyô no washi, (later released in the United States as Eagle of the Pacific), in which Yamamoto was portrayed by Denjirô Ôkôchi.

The 1960 film The Gallant Hours depicts the battle of wits between Vice-Admiral William Halsey, Jr. and Yamamoto from the start of the Guadalcanal Campaign in August 1942 to Yamamoto's death in April 1943.

In Daiei Studios's 1969 film Aa, kaigun (later released in the United States as Gateway to Glory), Yamamoto was portrayed by Shôgo Shimada.

Award-winning Japanese actor Toshiro Mifune (star of The Seven Samurai) portrayed Yamamoto in three films:
 * Rengo kantai shirei chôkan: Yamamoto Isoroku (1968) (later released in Canada and United States as Admiral Yamamoto),
 * Gekido no showashi 'Gunbatsu'  (1970) (lit. "Turning Point of Showa History: The Militarists"), and
 * Midway (1976) (where all of the Japanese scenes had English dialogue).

In Shūe Matsubayashi's 1981 film Rengō kantai (lit. "Combined Fleet", later released in the United States as The Imperial Navy), Yamamoto was portrayed by Keiju Kobayashi.

In the 2001 film Pearl Harbor, a Jerry Bruckheimer-produced epic, Yamamoto was portrayed by Oscar-nominated Japanese-born American actor Mako Iwamatsu. Like Tora! Tora! Tora!, this film also features the sleeping giant quote.

The most recent film to feature Yamamoto is Toei's 2011 war film Rengô kantai shirei chôkan: Yamamoto Isoroku (聯合艦隊司令長官 山本五十六), in which Yamamoto was portrayed by Kōji Yakusho.

Alternate history
In the 1993 OVA series Konpeki no Kantai (lit. Deep Blue Fleet), the original timeline proceeds until Yamamoto's death in April 1943. However, instead of dying in the crash, Yamamoto blacks out and suddenly wakes up as his younger self, Isoroku Takano, after the Battle of Tsushima in 1905. His memory from the original timeline intact, Yamamoto uses his knowledge of the future to help Japan become a stronger military power, and eventually launching a coup d'état against Hideki Tōjō's government. In the subsequent Pacific war, Japan's technologically advanced navy decisively defeats the United States, and grants all of the former European and American colonies in Asia full independence. Later on, Yamamoto convinces Japan to join forces with the United States and Britain to defeat Nazi Germany.

In the 2004 anime series Zipang, Yamamoto (who is voiced by Bunmei Tobayama) works to develop the uneasy partnership with the crew of the JMSDF Mirai, which has been transported back sixty years through time to the year 1942.

In Douglas Niles' 2007 book MacArthur's War: A Novel of the Invasion of Japan (written with Michael Dobson), which focuses on General Douglas MacArthur and an alternate history of the Pacific War (following a considerably different outcome of the Battle of Midway), Yamamoto is portrayed sympathetically, with much of the action in the Japanese government seen through his eyes, though he could not change the major decisions of Japan in World War II.