Japan’s Doomed Plans to Invade and Occupy Hawaii

Japan’s greatest strategic mistakes of World War II were its sneak attack on Pearl Harbor and failure to follow up that attack with destruction of the Pacific Fleet’s oil supplies, submarine base, shipyard, and drydocks. But was its failure to invade Hawaii a third strategic blunder? And could it have successfully carried out such an invasion?

The conventional narrative on the Pacific War has it that Japan never intended to invade Hawaii. This view asserts that the Japanese leadership felt Hawaii was too difficult to capture and retain and that it was, in any case, outside the desired limits of the Greater East Asia Co-Prosperity Sphere.  However, we now know that Hawaii was in fact explicitly included within the Sphere in both public and classified wartime documents. Indeed, the below map of Hawaii, created in 1943, explicitly shows that Hawaii had been envisioned in the Sphere.

On 7 December 1941, Japan achieved Admiral Isoroku Yamamoto’s goal of destroying most of the Pacific Fleet. After the attack, false reports of Japan’s invasion terrified residents of Oahu. The radio reported Japanese paratroops in the hills and transports offshore. Accounts of beach landings swept Oahu (“Saboteurs Land Here,” headlined the Honolulu Advertiser the next morning). On 9 December, Chief of Naval Operations Harold Stark cautioned Admiral Husband Kimmel, commander of the Pacific Fleet, to expect “additional attacks” and “initial occupation of islands other than Oahu including Midway Maui and Hawaii.”¹ Ten days later, Secretary of the Navy Frank Knox worried that Hawaii was not “safe from capture” and could not “guarantee that landings by Japanese troops [would] not be made.”² Paper currency was soon overprinted with “HAWAII,” rendering it worthless if Japan invaded.

All that protected U.S. interests in the Pacific were its three aircraft carriers that were fortuitously at sea during the attack. Hawaii was nearly defenseless against invasion. Nevertheless, Japan did not invade Hawaii as it soon did in the Philippines and Singapore. Had Japan successfully done so, it could have occupied the entire Pacific.

Professor John J. Stephan, a scholar fluent in Japanese, wrote about Japan’s aspirations to colonize Hawaii in Hawaii Under the Rising Sun: Japan’s Plans for Conquest after Pearl Harbor. As aforementioned, Japan had long seen Hawaii as part of its Greater East Asian Co-Prosperity Sphere. Before that term was even coined, as early as the 1870s, Japanese Foreign Secretary Taneomi Soejima reportedly “considered taking over the [Hawaiian] Islands.”³ In 1889, Japan prepared a secret 100-year plan to take over “American and British possessions in the Pacific, including Hawaii.”⁴ Japanese activist Keishiro Inoue “urged throughout the 1890s that Japan must rule Hawaii in order to protect itself in the Pacific.”⁵

These plans were fueled by the large number of Japanese who had emigrated to Hawaii to work in the sugar industry. From the late 1800s to the mid-20th century, the Japanese became Hawaii’s largest ethnic population, 160,000 strong by 1941.⁶ Tokyo regarded these expatriates as a form of territorial expansion, if not a forerunner of occupation.

By the 1890s, Hawaii’s leaders who overthrew the Hawaiian monarchy knew that “Hawaii was fair game for some colonial power, and rather than see their investments . . . fall under control of England, France, Germany, or Japan . . . they opted for a permanent tie with America through Annexation.”⁷ Japan opposed annexation. Its minister in Washington, Toru Hoshi, disingenuously assured Secretary of State John Sherman that “Japan ‘did not have and never did have’ designs upon the integrity and sovereignty of Hawaii.” In fact, Hoshi had recommended to the Japanese Foreign Minister that, to prevent annexation, “a strong naval armament should be at once dispatched for the purpose of occupying the islands by force.”⁸

Japan’s warship Naniwa was sent to Honolulu to discourage annexation. But that hastened passage in part to keep “Hawaii from Japan’s clutches.”⁹ As the prominent U.S. Senator George Frisbie Hoar declared before Congress, if Hawaii was not annexed, it “will fall . . . prey to Japan, not by conquest but by immigration. This result all parties agree that we must prevent.”¹⁰ Annexation in 1898 may have upset Japan’s plans of occupation, but it did not stop them.

Throughout the early 20th century up to and beyond the outbreak of World War II, Japan’s seizure of Hawaii was debated in novels, books, war games, and military circles in Japan and America. As early as 1907, Massachusetts Senator Henry Cabot Lodge feared Japan might “hoist their flag in Hawaii overnight.”¹¹

Two novels in 1909 predicted that outcome. Homer Lea’s The Valor of Ignorance opined that Japanese emigration to Hawaii was “political rather than economic” and that the number of former Imperial Japanese Army soldiers in Hawaii “exceeds the entire field army of the United States.” Lea concluded that Hawaii “can be seized from within and converted into a Japanese naval and military base so quickly that they will be impregnable to the power of this Republic.” In the book’s introduction, retired U.S. Army Major General J. P. Story lamented that “Japan now has sea supremacy in the Pacific” and that “never has there been on this earth so rich a prize, now so helpless to defend itself, as the Philippine and Hawaiian Islands.”¹²

In Ernest Hugh Fitzpatrick’s novel The Coming Conflict of Nations, or the Japanese-American War, Japan slipped 30 regiments to Hawaii under the guise of laborers. “These regiments captured those islands, but only after considerable loss and desperate fighting.”¹³

The United States became so troubled about a future war with Japan after its victory in the Russo-Japanese war of 1904–05 that, between 1910 and 1914, Oahu was fortified by eight batteries of large caliber guns and mortars, 26 antiaircraft gun emplacements, and six magazines.¹⁴ In the 1920s, a 16-inch gun, “the most powerful cannon ever built in the United States,” was installed at Pearl Harbor.¹⁵

In his 1925 novel The Great Pacific War: A History of the American-Japanese Campaign of 1931-33, Hector Bywater depicted a sneak attack by Japan on the U.S. fleet in Pearl Harbor. While Japan did not invade, resident insurgents in the islands gained strongholds that were overcome at great cost. Interrogated, insurgents “declared they were acting under the orders of the Japanese government.”¹⁶ Japan’s Navy was so impressed by the book that it was adopted “for the curriculum at the Naval War College.”¹⁷ One author suggested that Bywater’s book so closely mirrored Japan’s later attacks that it might have influenced Yamamoto’s strategies.¹⁸

From 1913 to 1941, several Japanese novels romanticized war with America and the seizure of Hawaii. These included Nichi-Bei Kaisen Yume Mongatari (1913), Nichi-Bei Moshi Kaisen Seba (1914), and Nichi-Bei Senso Yume Monogatari (1921).¹⁹ The second novel asserted that “Hawaii could be captured more easily than could the Philippines.”²⁰ Commander Kyosuke Fukunaga’s riveting 1931 thriller Nichi-Bei Sen Miraiki included forewords by two Imperial Navy admirals. The foreword by Vice Admiral Nobumasa Suetsugu stated that “it would be simply splendid if the war turned out as Fukunaga imagines.”²¹

An author ironically opined that “One curious aspect was that in many of the Japanese novels the Japanese were defeated, while many American novels had the Americans ignominiously booted out of the Pacific.”²²

Arguments for Hawaii’s occupation were not limited to novelists. “As early as 1924, Imperial naval officers were publicly discussing how to take Hawaii by invasion.”²³ In 1924, Admiral Seijiro Kawashima argued that occupation of Hawaii was necessary in a future war with America. After destruction of the Pacific Fleet, Japan could land “Forty, sixty, or even a hundred thousand Japanese troops” along Oahu’s northwest shoreline.²⁴

In 1932, Commander Hironori Mizuno argued that “if Japan does not succeed in seizing Hawaii, it means that the war will be prolonged and that Japan will not be able to win.”²⁵ That year, naval strategist Chuko Ikezaki concluded that the most Japan could gain from a war with America was a draw that could be achieved only by destroying the U.S. fleet and seizing Guam, the Philippines, and Hawaii.²⁶ Admiral Kanji Kato was impressed; he wrote the author that “the sections about Hawaii were the finest part of the book, adding that as long as the  islands remained in American hands they would be ‘a cancer in the Pacific.’”²⁷

In 1940, journalist and Japanese intelligence officer Kinoaki Matsuo argued that by taking Hawaii, Japan would “probably force the Americans to the peace table.”²⁸

From 1923 to 1940, the U.S. Navy ran war games called “Fleet Problems” that were followed closely by Japan. Fleet Problem XIII in 1932 foretold the Pearl Harbor attack nine years later. The carrier USS Lexington (CV-2), under command of then-Captain Ernest King, the Navy’s future wartime commander, launched a sneak attack on Oahu on a “Sunday morning, inflicting what the umpires deemed serious damage on the defending force.”²⁹ Army officers reportedly cried foul “about the ‘legality’ of attacking on a Sunday morning.”³⁰ Japan’s War College studied the results and concluded that its military should consider opening a future war “by surprise attack from the air.”³¹

A year later, Fleet Problem XIV resulted in a successful “Japanese” attack and invasion.

While losing Hawaii to Japan in Fleet Problem XIV failed to awaken American military planners to the threat, its lessons were “used in planning the attack on Pearl Harbor” by Japan.³² Indeed, on 29 November 1940, Japan’s Navy General Staff drafted a secret “Outline for the Establishment of the Greater East Asia Co-Prosperity Sphere” which “identified Hawaii as a target for annexation.”³³

Fleet Problem XIX in 1938 included a devastating “surprise attack on Pearl Harbor” that “set the stage for a successful invasion of Oahu by” Japan. The “overwhelming success” of the exercise demonstrated the military had failed “to mitigate issues exposed” by Fleet Problem XIII. Fatefully, Japanese observers in fishing boats off Oahu took “detailed notes.”³⁴

The last such-themed Japanese book published before the attack on Pearl Harbor, by journalist Chu Saito, advocated occupying the Big Island of Hawaii, followed by invasion of Oahu.³⁵

Admiral Yamamoto first officially proposed to attack Pearl Harbor in January 1941, as essential to giving Japan some breathing room of six months to one year.³⁶ During the planning phases in the summer of 1941, two of Yamamoto’s senior staff officers and Commander Minoru Genda “were contemplating not just an attack on Pearl Harbor but an invasion of Hawaii . . . immediately after the Pearl Harbor strike.”³⁷ Genda believed that “without taking and holding Oahu, Japan could not hope to win the war.”³⁸

War games of the Pearl Harbor attack were held 5–17 September 1941. After listening to opposing arguments, and despite his having advocated for an invasion of Hawaii in 1928, Yamamoto “decided that no landing on the island of Oahu should be attempted” as part of the attack.³⁹

Two days after the attack, Yamamoto changed his mind. On 9 December 1941, perhaps because he realized that the failure to seize Oahu had been a strategic mistake, Yamamoto “ordered his staff to prepare plans for the invasion of Hawaii.”⁴⁰ His chief of staff, Rear Admiral Matome Ugaki, became “a vociferous champion of a Hawaii invasion, code-named ‘Eastern Operation.’” Yamamoto’s goal was to draw out and annihilate the remaining Pacific Fleet, followed by invasion, which would become a bargaining chip for peace talks.⁴¹

Yamamoto also found an ally in Rear Admiral Tamon Yamaguchi, head of the Second Carrier Division, who developed the “Yamaguchi Plan.” It “consisted of seizing Midway, Johnston, and Palmyra [islands], imposing a blockade, and gradually tightening the noose of air and sea power around Oahu.” After invading the Big Island of Hawaii, “Oahu would eventually fall to an amphibious assault.”⁴²

The Yamaguchi Plan was initially opposed by the Japanese Army, which warned of “overextension” of equipment and supply.⁴³ Accordingly, by March 1942, the Navy settled on a purely naval Midway operation, followed by invasions of Johnston and Palmyra Islands in August, the Big Island of Hawaii in October, and Oahu in March 1943.⁴⁴ On 23 May 1942, the Army General Staff fell in line, issuing orders “to prepare for landings in Hawaii.”⁴⁵

Japan’s devastating losses at Midway scuttled the plans. Admiral Yamaguchi went down with his aircraft carrier Hiryu, along with the three other carriers lost there. Even after Midway, in the fall of 1942 General Douglas MacArthur feared Japan would soon “‘control the Pacific Ocean’” and “attack Hawaii” and some Japanese planners still dreamed of Hawaii under the rising sun.⁴⁶ But by 1943, setbacks in the Southwest Pacific “no longer made a Hawaii invasion a likely prospect.”⁴⁷

Could Japan have invaded Hawaii and supported its occupation? If it had, the course of the war would have taken a sharply different turn. The remaining Pacific Fleet “would have to retire to the West Coast, and Japan would dominate the central Pacific.”⁴⁸ There would have been no Midway. Could Doolittle have raided Tokyo? Could we have taken Guadalcanal?

Anthony P. Tully and Jonathan Parshall, authors of Shattered Sword: The Untold Story of the Battle of Midway, addressed the chances of seizing Hawaii in a web page titled “Invasion: Pearl Harbor!”⁴⁹ The authors debunk the idea, arguing that “the Japanese simply did not possess the amphibious and logistical wherewithal to assault, capture, and hold the Hawaiian Islands.”

They agree that if Japan had immediately followed up Pearl Harbor by invasion, “it is unlikely that the U.S. Army garrison there would have been able to put up a cohesive defense. So, the Japanese could, conceivably, have taken the Hawaiian Islands under these particular circumstances.” However, they conclude that “even if the Japanese wanted to, they didn’t have the ability to undertake both a Hawaiian operation and the intricate series of attacks which they envisioned unleashing against the Southwest Pacific.” The idea of such an invasion was therefore “risky to the point of lunacy.”

Fortunately, Japan never invaded Hawaii, and thus, its long-desired ambitions to do so from the 1870s through 1943 were doomed.