There is no doubt that given the juggernaut of the 1942 Japanese Army and Navy expeditions the Battle of Midway and the Guadalcanal Campaign were turning points in the war – each in their own different way. There is no shortage of books and online sources that can offer outstanding detail, commentary and analysis of the importance of Midway and Guadalcanal. But there are other events in the war that shaped the strategic and tactical vision of the Japanese military from the Spring of 1944 until the end of the war. The lessons learned from these events shaped the Japanese plan Ketsu-Go, the defense of the main home islands against allied invasion. The events were the Battle of Biak Island, Peleliu, the Battle of Philippine Sea, and the air Battle of Formosa.

The Battle of Biak

Most people have never heard of the Battle of Biak Island. Biak is not a large island. It is 45 miles long and 23 miles wide – about the size of the Hawaiian island of Moloka‘i. It is located near the western end of New Guinea and is part of the modern Indonesian Province of Papua. For reasons important to General Douglas MacArthur’s Southwest Pacific command, its capture was planned as a one week operation in late May 1944. The goal was to secure the “next island” in the overall advance that could support an airfield and extend MacArthur’s land-based air cover for scouting and operations.

The Southwest Pacific Command ran a separate intelligence operation from that of Admiral Nimitz’s Central Pacific Command. It was not that they did not share intelligence, but MacArthur preferred his own council – and his experience on intelligence was that it grossly overestimated or underestimated Japanese resistance or the suitability of the next step in the campaign to provide a locale for constructing a suitable airfield. This was his experience with intelligence reports associated with the campaigns of Hollandia and Atape, both of which failed to provide suitable ground for building an army air force base. The intelligence on Biak grossly underestimated the size of the Japanese garrison and its pre-invasion disposition. 

MacArthur’s attitude towards his own Intelligence Operation will come to the fore during discussions of the 1945 amphibious landings on the home Japanese islands.

In early 1944 at the Battle of Sio on New Guinea, Australian troops recovered a complete set of Imperial Japanese Army (IJA) code books and ciphers. Nonetheless, MacArthur’s “code breakers” missed communications indicating that the IJA had moved the 41st Division’s 222nd Infantry Regiment, an elite, battle-hardened and well-trained group to Biak just before the invasion. Because of an over reliance on aerial surveillance, the allies downplayed information that would have indicated efforts and materials to fortify caves and ridges inland, not the beaches—contrary to standard Japanese tactics, and contrary to Allied expectations.

Allied planners envisaged a week-long operation based on intelligence that there were approximately 2,000 Japanese troops defending the island. In fact, the Japanese garrison was 11,000-12,000 troops. 

Based on an appreciation of the Allied objectives (capturing the already built and operational airfields), island commander Colonel Kuzume Naoyuki focused his defensive plans away from the water’s edge. His plan was to let the Americans come ashore unopposed so that they would advance into the trap he had prepared for them utilizing a series of caves that were located west of Mokmer air field and to the east of Bosnek airfield. This defensive complex was intended to turn the area around the airfields into a honeycomb of defended caves and pillboxes filled with riflemen, automatic weapons, artillery, batteries of mortars, and a single company of light tanks. The western caves were connected by a series of underground tunnels that were constructed for fighting purposes. Kuzume also stockpiled these positions with ammunition, food, water, and other supplies, with several supply depots located around the eastern cave area, along with living quarters for the defenders. Water was limited on Biak and had to be strictly rationed by the US troops. Heat and humidity would take a heavy toll during the fighting.

Kuzume had no expectations other than he and his fighting force would ultimately be defeated but he carried out his orders as he well understood the larger objectives of inflicting casualties to weaken the will of the allied war fighters and the public back home.

Many online sources are available to provide the details of fighting on the island. Combat began with the May 27, 1944 landings and continued until June 22nd which marked the end of all organized resistance. Some 3,000 Japanese remained on the island attempting guerrilla-style warfare to no particularly successful end.  At the end of the campaign (late July) virtually all Japanese had died in combat or from disease and/or starvation. Allied losses were 460 killed in action with 2,440 additional non-lethal casualties the majority of which were disease related. Some 600 British Indian and Javanese forced laborers were also rescued.

Reports from Colonel Kuzume that reached IJA headquarters indicated that the strategic objectives of extracting mounting Allied casualties was a good strategy in the face of overwhelming allied ground forces, equipment, logistics support, air superiority, and control of the waters around Biak by allied naval forces. This strategy was implemented and faced the allied invasions of Peleliu (the Palau Islands) and the battles of Iwo Jima and especially Okinawa. They were intended – and we understood them to be harbingers of what awaited any attempted invasion of the Japanese home islands. In a different form, the same strategy was implemented at Leyte and Luzon in the Philippine Islands: unopposed landings with interior defenses in place to extract maximum allied casualties.

Peleliu

There is and will ever be controversy on the need to invade and secure Peleliu instead of bypassing the island to let its defenders “wither on the vine.” That is a topic for another post. For purposes of this series, Peleliu is important in that it exemplifies the changing strategy of the Imperial Japanese Army (IJA) in island invasions following the campaign on Biak.

The planners predicted that the island would be secured within four days. But IJA plans were that instead of defending the beaches, they focused on fortified inland positions, allowing U.S. forces to land relatively unopposed and then drawing them into a kill zone. It was a plan similar to Biak, but the terrain on Peleliu was radically different – more akin to that of Iwo Jima and Okinawa. The island’s central highlands (Umurbrogol ridges) became the core of Japanese defense. The coral ridges were honeycombed with over 500 caves, interconnected by tunnels that allowed troops to move, reinforce, and resupply without surfacing. Positions included machine gun nests, mortar pits, anti-aircraft guns, and artillery camouflaged and embedded into the ridges. Many caves had steel doors and ventilation, enabling troops to survive prolonged bombardments. The “four day” operation began on 15 September 1944 and lasted until 27 November 1944 when the island was declared secure. Nonetheless the  Army’s 81st Infantry Division remained engaged on the island until the end of organized Japanese resistance on 18 January 1945. Even then, a Japanese lieutenant with 26 infantry soldiers and 8 sailors held out in the caves on Peleliu until 22 April 1947, only surrendering after a former Japanese admiral convinced them the war was over.

The heavily outnumbered Japanese defenders put up stiff resistance, 98% fighting to the death in the name of the Japanese Emperor. The island became known in Japanese as the “Emperor’s Island” and held up as an example of the true spirit of the Japanese fighting forces.

The 1st Marine Division, the “Old Breed”, suffered a KIA and casualty rate that was unmatched among Allied forces during the war. When the men of the Army 81st Infantry Division relieved the “Old Breed” they saw men stumbling forward, their eyes sunken and glazed over with what became known as the “2,000 yard stare”, moving forward like zombies. Episodes 6 and 7 of the mini-series, “The Pacific” capture this experience. After the battle, Russel David, a private in the First Marines wrote about his experience of battle on Peleliu.

“I picked up the rifle of a dead marine and I went up the hill. I didn’t worry about death anymore. I’d resigned from the human race. I only wanted to be as far forward as any man when my turn came, As a fighting outfit the First Marines was finished.  We were no longer human beings. I fired at anything that moved in front of me, friend or foe. I had no friends. I just wanted to kill.”

On 24 November the Japanese force commander radioed Tokyo, “Our sword is broken and we have run out of spears”. He then burnt his regimental colors and performed ritual suicide. Prior to that IJA headquarter had been well informed about the “success” of the Peleliu strategy as a lethal strategy against any invasion of the home islands.

The Battles of Philippine Sea and Formosa

While the name might indicate a ship-to-ship engagement, the first two days of the conflict were fought in the skies in the area of the Marianas Islands. Just a few weeks after the start of the Biak landings, the massive Task Force 58 under the command of Admiral Raymond Spruance, began landings on Saipan. The importance of Saipan is covered in a later post focused on that battle. In short, were the allies to capture Saipan and neighboring Tinian, the Army Air Force B-29 Superfortress bombers would be in range of the main Japanese home islands.  A bombing campaign would (and did) begin.

From the very start of the conflict in December 1941, the Japanese war plan had been to inflict such substantial losses on the allied forces so that the U.S. public would become war weary and the American government would be convinced to sue for peace and allow Japan to keep its conquests. A central element of the plan was Japan’s ability to project naval power through its aircraft carriers and battleships. However, the Imperial Japanese Navy (IJN) had suffered extensive air wing losses at aircraft carrier battles such as Coral Sea, Midway, and the Solomon Islands campaign of 1942–43. The losses were not only in aircraft carriers, but in skilled carrier pilots. After the Solomons campaign it took nearly a year for the IJN to reconstitute their air groups.

Early in the war the United States had only one operational aircraft carrier, USS Enterprise. By June 1944, Task Force 58 approaching Saipan included 7 fleet carriers and 8 light carriers with a combined fleet air group of 900 planes. The Japanese came to the conflict with 3 fleet carriers, 6 light carriers with a naval air wing of 450 aircraft – but with 300 land based aircraft on Tinian and Guam. Not only were the numbers in favor of the U.S. forces, but the capabilities of the U.S. pilots was, on the whole, vastly superior to their counterparts. This was due in part to the efforts of U.S. submarines sinking merchant oil tankers thereby limiting the aviation fuel oil available for training Japanese pilots. Some reports indicated that the average IJN pilot entered the battle with 200-300 hours of flying and with little to no combat experience. The average U.S. aviator had 800-900 hours of flying, much of it combat.

As before, there are plenty of online sources that detail the ebb and flow of the air campaign of Philippine Sea fought over two days. After the second day of the battle, IJN losses totaled three carriers, more than 350 carrier aircraft, and approximately 200 land-based aircraft – and their aircrews. In the five major “carrier-on-carrier” battles, from the Battle of the Coral Sea to the Battle of the Philippine Sea, the IJN  lost nine carriers, while the USN had lost three. The aircraft and trained pilots lost at Philippine Sea were an irreplaceable blow to the already outnumbered Japanese fleet air arm. The Japanese carrier air groups lost 90 % of their force in two days. The Japanese had only enough pilots left to form a single air group for one light carrier. 

Though still relatively unknown to general audiences of World War II history, the Formosa Air Battle (Oct. 12-16) was the single largest air-sea battle of the Pacific war. Japan committed a greater mass of air power to this battle—1,425 army and navy aircraft over the course of one week—more than anything the U.S. Navy had faced prior. In fact, the Japanese air force participating in the Formosa Air Battle was multiple times bigger than the carrier air formations encountered during the more well-known Battle of the Philippine Sea.

Overall the Japanese lost ~600 airplanes and crews. U.S. losses were 89 aircraft, however, almost all the U.S. pilots were rescued. Surviving Japanese pilots returned with tales of a stunning victory. It was reported that practically the whole U.S. Third Fleet had been sunk and the American carrier force was left in shambles with virtually all fleet carriers sunk.

The “victory” was celebrated by the IJA aviation wing, though the IJN command was initially skeptical of such reports. The “victory” narrative was carried forward by the military  members of the cabinet until it reached Emperor Hirohito. He congratulated the Navy and Army for their success and declared a national holiday. Newspapers in particular trumpeted these claims, repeating that the U.S. task force was broken and in retreat. Even those unconvinced members of the IJN, up to and including Admiral Toyoda of the Combined Fleet, believed some kind of victory had been achieved off Formosa. It was trumpeted as the “decisive battle” envisioned in Japan’s war plan, Kantai Kessen (“Decisive Battle Doctrine”) – not to defeat Allied forces, but to bring the United States to the negotiating table.

Consider how this affects the problem for war termination. Virtually all wars end when one side realizes it has been defeated. From civilian to Emperor, there does not seem to be the realization their defeat is inevitable at this point – nor that the Allies are not interested in armistice or negotiated settlements. The Allies intend to win this war and prevent the next one.

A Sea Change in Naval Aviation Strategy and Tactics

This marked a shift from offensive Naval aviation operations as seen early in war to a purely defensive posture. With battle losses at Philippine Sea, the fall of Saipan, Tinian and Guam were only a matter of time. Japanese planners knew that the Allied forces would next focus on the Philippine Islands themselves. The Japanese military believed its only hope was to inflict such severe losses on the landing fleet that the Americans could be drawn into negotiations with the goal of leaving the Home Islands intact and still maintain control of some of the territories in East Asia, especially those key to import of critical raw materials.

From this situation was born the Kamikaze, “divine wind” (officially Shinpū Tokubetsu Kōgekitai – Divine Wind Special Attack Unit). They were a part of the Japanese Special Attack Units of military aviators who would fly suicide attacks against Allied naval vessels in the closing stages of the Pacific campaign of World War II. 

The attacks began in October 1944 in the shadow of the losses at Philippine Sea. Japan had lost decisive battles key to their overall strategy. The corps of skilled aviators was decimated and replacements could not be trained fast enough. Japanese aircraft were becoming outdated with the introduction of new allied fighter planes. Japan had lost command of the air and sea. These factors, along with Japan’s unwillingness to surrender, led to the institutionalization of kamikaze tactics as a core aspect of Japanese air warfare strategy as Allied forces advanced towards the home islands.

In this atmosphere of strategic desperation, what appeared to the Western nations as erosion of psychological and doctrinal barriers to deliberate suicide was more likely a manifestation of the Bushido code. A tradition of death instead of defeat, capture, and shame was deeply entrenched in Japanese military culture – loyalty to the Emperor and honor until death. This was not limited to aircraft. In addition to kamikazes, the Japanese military also used or made plans for other Japanese Special Attack Units, including those involving Kairyu (submarines), Kaiten (human torpedoes), Shinyo (speedboats), and Fukuryu (individual divers). 

Bushidō code and militarist ideology had long glorified death in service to the emperor. The loss at the Philippine Sea helped shift this from a theoretical ideal into military tactics.

The Battle of Biak Island, Peleliu, and the Battles of Philippine Sea and Formosa changed the nature of warfare in the Pacific.

Image credit: various photographs from Naval Aviation Museum, National World War II Museum, and US Navy Archives.

The island of Saipan in part of the Mariana Islands lies southeast of Tokyo at a distance of 1,450 miles. Its capture was always part of War Plan Orange because of its strategic importance. The capture of the Marianas (Saipan, Tinian, Rota, and Guam) ensured an open sea lane for logistics support from the mainland United States. Guam became one of the major supply depots in the Pacific from August 1944 to the war’s conclusion. Even today every branch of the US military operates out of Guam – notably Submarine Squadron 15/Los Angeles Class fast attack submarines and Seal Team One.

However the real prizes were Saipan and Tinian. Their location allowed the US and Allies to build multiple airfields for the B-29 Superfortress bomber which initiated sustained bombing of Tokyo and the Japanese home islands for the first time.

While Guam had been a U.S. colony, Saipan had been a Japanese colony since it was ceded to Empire of Japan by the League of Nations as a part of its mandated territory of the South Seas Mandate that transferred all Pacific territories to WWI allies – of which Japan technically was one.

In the best of scenarios, the two warring factions agree to meet in the open away from cities, away from civilians, and decide the end result without involving the innocents. Scenes from “Braveheart” come to mind. But even then the winning army goes on to lay siege to the castle while ransacking towns and villages. Whatever the victor’s intent, war has its own purpose and passion. Revenge and retribution seem more powerful than reconciliation. And some things can not be unseen or forgotten by war fighters or witnesses.

The goal of this post is to make the reader aware of one element that was a critical factor in the decision whether (and how) to invade the Japanese home islands in the autumn of 1945 and spring of 1946. But also to let us remember it is individuals who fought the wars in our name and in many cases faced unspeakable evil. They carry the scars of combat – images and memories that challenge their humanity. Catholic just war teaching acknowledges the moral weight is most often borne by those who carry arms. While the national leaders may determine that a war is just, the individual soldier carries the burden of action, decision, and consequence.The dual responsibility of the war fighter — obedience and moral discernment — can place the war fighter in situations of profound moral tension and leave them with life-long memories. The cost of war is carried beyond the battlefield: moral injury, post-traumatic stress, and a deep spiritual dislocation. The battlefield lingers in memory and emotion long after the fighting ends.

Such was the case of the U.S. Marines who witnessed needless civilian deaths on the island of Saipan. While civilians caught in the cross fire is perhaps an inevitability of modern warfare, the intentional blurring of the difference between soldier and civilian by an enemy crosses a line of moral behavior and essential humanity. The disregard of civilian lives by the Imperial Japanese Army (IJA) before the June 1944 invasion of Saipan is well documented. The scope of civilian deaths at the hands and instigation of the IJA staggers the imagination. 

Civilian deaths caused by Japanese military actions from 1936 to 1945 

To be sure it is difficult to account precisely due to incomplete records, wide geographic scope, and ongoing historical debate. However, historical estimates, based on scholarship, war crimes tribunals, and national archives, provide the following approximate figures:

The above information is provided, not as a means of establishing the basis for punishing the Nation of Japan as punitively as possible nor to justify a wholesale invasion of Japan’s home islands. The post-war tribunals addressed the war crimes and those responsible. But it is presented to reveal the mindset, practice and history of field-level commanders in the Imperial Japanese Army (IJA), especially those operating in the far-flung corners of the Japanese empire. 

Among the “junior officers” there was a history of rebellion, assasination, and “taking the initiative” in ways unimaginable in the allied armed forces. It is believed (not proven) that junior officers were most responsible for the July 1937 escalation of armed forces involvement from the incident at the Marco Polo Bridge that is considered the beginning of the Second Sino-Japanese War. 

Another  glaring example is the forging of orders given to Major General Tomitarō Horii to cross the virtually impassable Owen Stanley Range via the Kokoda Track to attack Port Moresby in Papua New Guinea. The attempt resulted in ~5,000 deaths from combat, disease, exposure, or starvation. Among them were scores of forced laborers from Korea and China.

A concern of the Allied Leaders in July 1945 was the reaction of the IJA outside the home islands in the event of invasion of their homeland. Would there be retaliatory strikes against local civilian populations in Japanese occupied territories? Also, in the event of Japanese surrender, would the IJA surrender arms inside and outside of Japan? Mutinies initiating within the ranks of the IJA had been well documented.

Civilian non-combatant deaths did not become a point of US military experience until the invasion of Saipan in June 1944. The experience of Saipan not only greatly clouded the question of whether “civilian non-combants” were a separate and distinguishable group, but also left indelible marks on the US Marine witnesses. The experience of the invasion of Iwo Jima and Okinawa added to and amplified the Saipan experience. All this justifiably raised the issue of what were the expectations in an invasion of the main home islands as regards “civilians.” 

Image credit: various photographs from Naval Aviation Museum, National World War II Museum, and US Navy Archives.

Prior to the attack on Pearl Harbor there was no blockade of Japan. Five months before the Pearl Harbor attack the Dutch, English, and Americans announced an embargo on the sale of oil, steel and scrap metal. An embargo is not an act of war; it is an economic and political tool, enforced primarily through laws, regulations, and diplomatic pressure. Its intent is always to solicit acceptable behavior, which in July 1941 meant for Japan to cease its war actions in Manchuria, China, and Indonesia.  All this before Pearl Harbor.

A naval blockade is an act of war. Naval blockades come in two forms: the embargo of selected items and a complete shutdown of ships with cargo of any type. World War I was enmeshed in the endless slugfest of trench warfare when Britain instituted a complete naval blockade to cut off Germany’s access to food, raw materials, and supplies. The Royal Navy blockaded the North Sea, intercepting ships heading to Germany and occupied countries in Europe. This led to severe food shortages and malnutrition among German civilians. It is estimated that 400,000–750,000 German civilian deaths were due to starvation and disease. The blockade contributed significantly to domestic unrest and the eventual German collapse in 1918. The blockade continued even after the armistice (Nov 11, 1918) until the signing of the Treaty of Versailles (June 28, 1919).

Germany’s unrestricted submarine warfare in WWII was an attempt to blockade England from receiving needed supplies including food. Before the war, 70% of Britain’s food supply was imported. In 1942, as German U-boat attacks during the Battle of the Atlantic reached their peak, imports of meat, sugar, fruit, and cereals were drastically cut. This led to severe rationing. Britain successfully avoided famine through a mix of rationing, domestic production, and American aid which began to increase significantly by late 1942 as the Battle of the Atlantic began to turn in favor of the allies.

While the U.S. submarine force in the Pacific is credited with sinking one Japanese super aircraft carrier, two fleet carriers, two escort carriers, four heavy cruisers and other combatants. Their role as a naval combatant against Japanese fleet units was always going to be limited: aircraft carriers had a speed of 28-40 knots; a submerged WWII submarine could make only 3-4 running her engines on battery power. The real contribution of the submarine force was against merchant shipping.  By the end of the war, U.S. submarines had sunk approximately 50% of all Japanese merchant shipping.

While perhaps familiar to many of the readers, it might be useful to offer a brief summary of the early months of the War in the Pacific. In a modification of Japan’s war plan, Kantai Kessen, on December 7, 1941, Japan launched a surprise and devastating attack on the U.S. Fleet at Pearl Harbor, Hawaii. The goal was the decisive battle that would neutralize the U.S. Pacific Fleet and secure freedom of action for the planned offensive in Southeast Asia. The results of the attack are well known, but the battle was not decisive for three major reasons: the U.S. aircraft carriers were not in port, the fuel depot was not attacked, nor was the Pearl Harbor Naval Shipyard.  Had the depot and shipyard been destroyed the fleet would have withdrawn to the west coast affording incalculable time for Japan to advance and more firmly secure its war gains.

Japan rapidly expanded across the Pacific and Southeast Asia in a coordinated offensive:

• Philippines: Attacked within hours of Pearl Harbor; U.S. and Filipino forces withdrew to Bataan and Corregidor, ultimately surrendering.
• Guam and Wake Island: Guam captured quickly; Wake resisted before falling on December 23.
• Hong Kong: fell to Japan on December 25, 1941.
• Rabaul (New Britain): captured in January 1942, becoming a major forward base.
• Burma: Japan advanced to cut off the Burma Road to China – it was the main overland supply route by which the United States and British Empire provided military aid to Nationalist China in its war against the Japanese – a war initiated in 1937.
• Malaya and Singapore: Japanese forces advanced swiftly down the Malay Peninsula, capturing Singapore on February 15, 1942
• Battle of the Java Sea (Feb 27, 1942): the Allied ABDA Command (American, British, Dutch, Australian) lost the majority of its sea power leaving Java and the Dutch East Indies open to Japanese invasion
• Dutch East Indies (Indonesia): Seized for its oil resources; Java fell by March 1942.
• Doolittle Raid (April 18, 1942): U.S. bombers struck Tokyo and other cities, a psychological blow to Japan and a factor in their decision to strike Midway.
• Battle of the Coral Sea (May 4–8, 1942): a strategic Allied victory in that it stopped the invasion of Port Moresby, New Guinea – a gateway to northern Australia.

Japan planned Operation MI, an operation to lure the U.S. Navy into a decisive battle by attacking and occupying Midway Atoll, a key American base northwest of Hawaii. Their hope was for a decisive Kantai Kessen-style battle that would destroy the last Pacific assets: U.S. aircraft carriers. Victory would cement Japanese strategic dominance in the Pacific.

Station Hapo, Hawaii – using signal intelligence vs. pure code breaking – learned of the attack on Midway and in an “all-in” gamble, Admiral Chester Nimitz committed the U.S. carries to the action that stopped the tide of Japanese advance in the Pacific. At the Battle of Midway (June 4–7, 1942) Japan suffered a catastrophic defeat, losing four fleet carriers and shifting the balance of naval power in the Pacific.

War Plan Orange – greatly revised, but with key elements intact – was now free to work its way westward to prosecute the War in the Pacific on new terms and conditions.

I do not plan to work step-by-step through the war in the Pacific. I will leave the heroic battles of places such as Guadalcanal and Tarawa for you to research. As well, I do not discuss the 1942 naval engagements such as Savo Island, Eastern Solomons, Cape Esperance, Santa Cruz, sea battle of Guadalcanal and Tassafaronga – all in the defense of the Marine Division on the island of Guadalcanal. I would note that the US Navy suffered more killed-in-action than the US Marines during the Guadalcanal campaign.

Moving ahead, I will highlight key several military actions that reveal fundamental shifts in Japanese military tactics and strategy. These shifts will shape planning for an invasion of the Japanese home islands in 1945-1946, an endeavor whose potential for the loss of life – military and civilian – defied estimation.

By the end of 1942 the advance of the Japanese has been stopped. The advent of 1943 would see the allied forces move from the defense to offense. The might of American industrial power in shipping building (combatants and merchants), aircraft, ammunition, and every aspect of logistics support would “come fully on line” as the work of the US submarines interdicted needed critical war supplies from Southwest Asia to Japan.

As noted in the first post, this series is not aimed at concluding with “the atomic bomb was the lesser of all the evils about to be faced.” It is intended to hopefully provide a correct historical understanding available to the 1945 leadership who faced the impossible task of ending a war with an intractable enemy and not repeating the armistice of 1919 that became the next war. 

Image credit: various photographs from Naval Aviation Museum, National World War II Museum, and US Navy Archives.

All militaries conduct war games as a means of preparedness, readiness, strategic deterrence, intergovernmental planning, and to provide concrete options to civilian leaders in support of their policy and national security objective. Peacetime planning allows the military to anticipate potential threats and develop responses, systems, and forces before a crisis emerges. 

War Plan Orange was one of several plans outlining the United States military’s detailed strategy for a future war. The plans were developed as early as 1919. War Plan Orange was the plan for a potential war in the Pacific. Some have argued that War Plan Orange is evidence that the United States always intended to begin a war with Japan; the logic being why else would you plan a war? The United States had found itself completely unprepared for the First World War and so even as it stood down its wartime military, planning for future wars began. Japan was the natural candidate given its evolving militarism and colonial expansion undertaken by Japan that began in the late 1860s with the Meiji Restoration. This evolution inexorably continued up to and into the start of World War II.

The Plan was part of the Navy War College curriculum. Virtually every senior naval leader in the Pacific had studied Plan Orange and contributed to it as new circumstances, technology, and situations arose. As one historian noted: “it was part of their DNA.”

The effect of the military development efforts associated with the Meiji Restoration were realized in the first Sino-Japanese War (1894–1895). Victory over China ceded Japan the island of Taiwan and established Japan as a regional power. That status was solidified during the Russo-Japanese War (1904–1905) fought over rival imperial ambitions in Manchuria and the Korean Empire. Japan’s victory shocked the West and solidified its status as a major military power – and especially as a naval power with the utter defeat of the Russian fleet at the Battle of Tsushima – a battle that would shape Japan’s own war planning. 

In 1910 Japan formally annexed Korea. A few years later, Japan was technically a member of the World War I allied alliance against Germany. Japan’s military, taking advantage of the great distances and Imperial Germany’s preoccupation with the war in Europe, seized German possessions in the Pacific (Micronesian islands) and German holdings in China, but there was no large-scale mobilization of the economy needed to support their ambitions. Politically, the Japanese Empire seized the opportunity to expand its sphere of influence in China, and to gain recognition as a great power in postwar geopolitics.