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.”

Plan Orange’s foundation was in keeping with the theory of Alfred Thayer Mahan, naval officer, historian and author of the book “The Influence of Sea Power upon History, 1660–1783.”  A key aspect of his theory was that global wars would be decided by decisive engagements between opposing surface fleets – battleships, cruisers, and destroyers. It was the touchstone of both pre-war Japanese and US naval war planning. The over reliance on Mahan led to shortsightedness about the role of evolving aircraft carriers, naval aviation and submarines – and even cross-Pacific logistics support.

From 1919 the plan underwent many revisions, especially after the Washington Naval Treaty (1922), which limited naval armament. Nonetheless, the Plan was always updated with an eye to the rise of Japanese militarism and expansion in Asia. The change in Japan was a complex process driven by economic pressures, nationalist ideology, strategic ambition, and a growing belief in  “manifest destiny” of Japan’s role in Southeast Asia. It unfolded over half a century, culminating in a series of aggressive moves that destabilized East Asia and set the stage for the war in the Pacific. War Plan Orange evolved based on our understanding of the strategic intentions of the nation of Japan.

At the same time Japan’s own war plan, Kantai Kessen (“Decisive Battle Doctrine”), was predicated on a decisive fleet action echoing their victory over the Russian Navy at the 1905 battle of Tsushima. Their plan assumed the enemy force would be the United States. While the plan did not assume an initial attack by the Japanese, it did speak of goading the U.S. into conflict with concerns about the Philippines. An outline of the plan was:

• The U.S. would send its main fleet westward from Hawaii and California to confront Japan.
  • Japan would conduct an initial offensive, rapidly seizing territory (such as the Philippines, Dutch East Indies, and others) to create a defensive perimeter and force the U.S. into long supply lines.
• Japan would then wait for the U.S. fleet to approach, gradually weakening it with submarine and carrier based air attacks as it crossed the Pacific.
• The decisive event would be a massive fleet engagement near Japanese home waters, where the Imperial Japanese Navy’s fleet would destroy the weakened U.S. fleet in a single, decisive naval battle.

Plan Orange’s essential elements were

• War would be initiated when Japan seized the U.S. Pacific territories like the Philippines and Guam early in a conflict.
• The U.S. fleet, based in Hawaii or California, would respond. (Note: the Pacific fleet headquarters were moved to Pearl Harbor in May 1940 in response to Japanese expansion in the western Pacific)
• The U.S. fleet would hold defensive positions, gather strength, and then launch a massive naval thrust across the central Pacific to take back U.S. possessions and bring Japan to battle. (Note: the plan never anticipated the long distance strike at Pearl Harbor)
• Expectations of a decisive naval engagement, much like the Battle of Tsushima (1905), where the superior fleet would crush the enemy in a single encounter. 

Over time realizing the problems of long range logistic support in recapturing any territories and islands, the plan evolved to include:

• Enhanced defense of U.S. outposts (Philippines, Guam) as a holding action until  the Pacific Fleet could mobilize.
• The Navy and Marine Corp would advance by retaking islands, establishing forward bases and implementing secure trans-Pacific supply lines.
• Post the “decisive” sea battle, there would be blockade and bombardment of the Japanese home islands to force a full and final surrender.

While the defense of U.S. territories was not effective and the Pacific fleet was virtually crippled by the Dec 7th attack on Pearl Harbor, in broad outlines, the planners on both sides on the Pacific conflict were accurate in the manner by which the war in the Pacific would be prosecuted.

What is key to remember is that the Japanese depended on the decisive battle to convince the U.S. to sue for peace. It was never their objective to defeat the United States per se, but only to negotiate an armistice that resulted in the western nations accepting Japan’s “sphere of influence” in East Asia.  

Few Japanese leaders had in-depth understanding of the United States, its natural resources, or its industrial base.  One exception was Admiral Yamamoto, the architect of the Pearl Harbor attack. He understood the need for the “decisive battle” at the beginning of armed conflict so that an armistice was quickly accomplished. He knew that Japan would lose a war of attrition once the industrial power of the United States kicked into high gear.

Note: In the movie “Tora! Tora! Tora!” Admiral Yamamoto, after Pearl Harbor, is shown to remark “I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve”  While it was quite prophetic, it was also the imagination of the screen writer. There is no record of the Admiral making such a remark.

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