World War II: Pacific Theater Summary

  • Last updated on November 10, 2022

The Empire of Japan represented the Axis Powers in the Pacific theater of World War II. The Japanese war began in China, but after Japan’s massive attack on the Pacific Islands between Asia and Hawaii in December of 1941, it faced the United States. The Americans responded to their initial Pacific losses with an “island-hopping” strategy, slowly regaining control of the Pacific. Japan refused to surrender, however, until the United States deployed nuclear weapons, dropping atomic bombs on the Japanese cities of Hiroshima and Nagasaki.

Summary of Event

The conflict in World War II’s Pacific theater had its origins in the geopolitical struggle between the United States and Japan U.S.-Japanese relations[U.S. Japanese relations] Japanese-U.S. relations[Japanese U.S. relations] that extended back into the last decades of the nineteenth century. The United States began to develop its global reach during the presidencies of William McKinley McKinley, William and Theodore Roosevelt Roosevelt, Theodore . Under their administrations, America became a major participant in the new world system and sought to establish itself as a dominant power in the international struggle to control world markets and raw materials. World War II (1939-1945)[World War 02];Pacific theater [kw]World War II: Pacific Theater (July, 1937-Sept. 2, 1945) [kw]War II: Pacific Theater, World (July, 1937-Sept. 2, 1945) [kw]Pacific Theater, World War II (July, 1937-Sept. 2, 1945) World War II (1939-1945)[World War 02];Pacific theater [g]Pacific;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [g]Asia;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [g]Southeast Asia;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [g]Australia;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [g]Micronesia;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [g]South Pacific;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [g]Polynesia;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [g]United States;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [g]Japan;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [g]China;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [c]World War II;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [c]Military history;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] [c]Wars, uprisings, and civil unrest;July, 1937-Sept. 2, 1945: World War II: Pacific Theater[00010] Hay, John Kōki, Hirota Yamamoto, Isoroku Yamashita, Tomoyuki Nimitz, Chester W. MacArthur, Douglas [p]MacArthur, Douglas;World War II Kuribayashi, Tadamichi Ushijima,Mitsuru Buckner, Simon Bolivar, Jr. Truman, Harry S. [p]Truman, Harry S.;World War II

In East Asia, the nation most important to the economic security of the United States was China China;and U.S. trade[U.S. trade] . By the 1890’s, Russia, Japan, the United Kingdom, France, and Germany had begun to carve out spheres of influence in East Asia, and the McKinley administration began to fear that the United States would lose access to its valuable Chinese trade. John Hay, McKinley’s secretary of state, proposed the open door policy Open Door policy , which advocated equal access to this trade with China. This policy conflicted with a growing Japanese belief that Asia should be dominated by the strongest Asian power, Japan. The resulting Japanese-American tension was exacerbated when the Theodore Roosevelt administration arranged an informal diplomatic understanding with the government of Japan, known as the Gentlemen’s Agreement (1907) Gentlemen’s Agreement (1907)[Gentlemens Agreement] , that addressed the discrimination faced by Japanese American Racial and ethnic discrimination;Japanese Americans students in the California educational system. The Gentlemen’s Agreement ended the formal segregation of Japanese students in exchange for Japan’s promise to restrict the emigration of Japanese workers to America. Many Japanese regarded the Gentlemen’s Agreement as a racist slap in the face, and it increased anti-American feeling in Japan.

Japan’s Internal Struggles

The 1920’s was a decade of deep political unrest in Japan that centered on a power struggle between the military and the civilian government. In particular, a group of chauvinistic young army officers attacked the civilian government for what they perceived as its weak and incompetent handling of the nation’s diplomacy. They believed the government had disgraced itself by accepting the provisions of the two major treaties of the Washington Conference Washington Conference (1922) of 1922. They viewed the Five-Power Treaty Five Power Treaty (1922) , which assigned Japan the smallest ratio of battleships among the world’s major naval powers, and the Nine-Power Treaty Nine Power Treaty (1922) , which protected the territorial integrity of China, as betrayals of Japan’s national security. These young army officers called for a military takeover Revolutions and coups;Japan Japanese military coup of 1936 of the government, and army death squads assassinated Assassinations and attempts;Japan a number of important Japanese officials. With the approval of the young militants, a former foreign minister, Hirota Kōki, became the new leader of the Japanese government. This marked a turning point in the history of Japan and placed the nation’s foreign policy directly in the hands of the military.





War with China

Once in control, the army began to finalize plans to invade China. World War II (1939-1945)[World War 02];Chinese campaign Second Sino-Japanese War (1937-1945)[Second SinoJapanese War] The invasion began in July, 1937. The Japanese military inflicted heavy casualities on the Chinese forces, and the Nationalist government was unable to stop the Japanese advance. Contrary to the Geneva Conventions, Japan’s military elite also targeted civilians. The most infamous example was the destruction of one of China’s great cities, remembered as the Rape of Nanjing Nanjing, Rape of (1937-1938) War crimes;Second Sino-Japanese War[Second SinoJapanese War] . Between mid-December, 1937, and early February, 1938, the Japanese army tortured and executed tens of thousands of military prisoners, raped in excess of 50,000 women, and killed thousands of civilians; conservative estimates place the overall death toll at 250,000.

Japan Joins the Axis

The United States initially reacted to the Japanese aggression through both diplomatic channels and public statements condemning the brutality of the Japanese military. By the early summer of 1940, the situation in Asia had deteriorated to such an extent that the United States placed an embargo on the sale of aviation fuel, lubricants, and scrap metal to Japan. This was a significant blow to the Japanese war machine, and the diplomatic tension between the two nations escalated significantly. Japan then reached out to its fascist counterparts in Germany and Italy; they signed the Tripartite Pact Tripartite Pact (1940) in September of 1940. This solidified the Axis alliance and gave the fascist Fascism militarists a global reach. Most historians agree that Japan wanted to use the Tripartite Pact as a strategic weapon against the possibility that the United States would intervene militarily in China. An alliance with the two European fascist powers would necessitate that the United States be willing to fight a multi-front war if it chose to stand up to Japanese aggression in Asia. The United States reacted to Japan’s new imperialist ambitions by placing greater restrictions on the export of oil and steel and by closing the Panama Canal to Japanese shipping.

War Plans Are Laid

As a result of these actions on the part of the American government, Japan decided that the U.S. military threat in Asia had to be neutralized. The geostrategic goals of the Japanese high command were to drive the United States from Asia and to obtain dominance over important geopolitical space, especially the resource-rich areas of East and Southeast Asia. Most important for the future of the Japanese Empire, the oil deposits in the Dutch East Indies and the strategic waterways, including the Strait of Malacca, would have to be brought under Japanese control. The main target of Japan’s military would be the destruction of the U.S. Pacific Fleet at Pearl Harbor. The essential goal of Japan’s military was to deliver a devastating knockout blow against United States forces stationed in Hawaii.

The Japanese plan to attack Pearl Harbor Pearl Harbor, Japanese attack on World War II (1939-1945)[World War 02];aerial assaults had its historical foundation in four military actions, one of which dates back to the first decade of the twentieth century, during the Russo-Japanese War Russo-Japanese War (1904-1905)[RussoJapanese War] . Military historians agree that the decisive action of that conflict was the Battle of Tsushima Tsushima, Battle of (1905) . In the Tsushima Strait, off the coast of Korea, the Japanese navy ambushed the Russian navy in a devastating attack, using a combination of naval gunnery and surface-to-surface torpedoes. It destroyed the Russian Pacific Fleet. The attack was so incapacitating that the Romanov Dynasty sued for peace. This outstanding military victory, in conjunction with the Japanese success in World War I World War I[World War 01] , developed a belief among Japan’s military elite that its forces could in fact defeat the military might of the Western industrialized nations.

Japanese admiral Isoroku Yamamoto also drew on more recent military events in planning for the attack on Pearl Harbor. In the early 1930’s, in reaction to the Japanese invasion of Manchuria, the United States conducted a series of war games testing the vulnerability of its strategic bases in Asia. In one such exercise, an American carrier force successfully launched an air attack against the U.S. fleet stationed at Pearl Harbor, and the account of this event impressed Admiral Yamamoto and his staff. Yamamoto was also influenced by the British use of carrier forces in the early months of World War II, when carrier-launched aircraft played a pivotal tactical role in the British victory against Italian forces in the Battle of Taranto Taranto, Battle of (1940) . The success of these naval actions helped convince Yamamoto that a surprise carrier-based operation could in fact cripple American forces and drive the United States from Asia.

The Attack on Pearl Harbor

For its part, the U.S. Intelligence Command World War II (1939-1945)[World War 02];military intelligence had been amassing a significant amount of information about the movement and buildup of Japanese forces in the Pacific region. By late November and early December, 1941, the U.S. military command, including General George C. Marshall Marshall, George C. [p]Marshall, George C.;World War II , concluded that Japan was in the process of amassing its naval, air, and ground forces to launch a major offensive in Asia. Despite repeated warnings of a possible attack, however, the tactical defense structure at Pearl Harbor was completely unprepared for the Japanese strike on the morning of December 7, 1941, and all the military equipment that could have been used to repel the attack had been left unstaffed; this enabled the Japanese military to devastate the American forces.

As destructive as the Japanese attack was, the most important targets, America’s three aircraft carriers, escaped the onslaught. These carriers and their accompanying fighters and torpedo bombers would play a major role in the United States’ naval victories in early 1942. Finally, for all of its great tactical success, most historians agree that this attack was a significant strategic blunder. The Japanese completely miscalculated the collective strength and resolve of the American people. Instead of pulling back to “fortress America” and suing for peace, the people united behind their president in a common effort to defeat the Axis alliance. The great industrial capacity of the United States—arguably the deciding factor in World War II—would allow the nation to create a war machine that the Japanese resource base simply could not match.

Japan Controls the Pacific

The attack on Pearl Harbor was just part of a much greater plan to occupy and control important geopolitical areas, to gain access to strategically significant resources, and to prevent counterattacks by antifascist forces. Within twenty-four hours of the initial attack, Japanese ground forces launched invasions of the American bases at Guam and Wake Island. Other military units moved against British and French forces in Indochina and captured Thailand. By January, 1942, the Japanese army had captured Manila, the capital of the Philippines, as well.

Then, under the leadership of General Tomoyuki Yamashita, the Empire of Japan attacked Malaya World War II (1939-1945)[World War 02];Malayan campaign . This military action was taken as a first step to gain control of the strategic city of Singapore. Singapore was located at the tip of the Malay Peninsula, and it held the geopolitical key to the control of both the Strait of Malacca and the Netherlands Indies (now Indonesia). World War II (1939-1945)[World War 02];Indonesian campaign The Strait of Malacca is one of the most important waterways in the world. Geopolitically, this strategic choke point controlled the avenues of movement among the four major islands of Borneo, Celebes, Sumatra, and Java. Domination of this important area would allow the Empire of Japan to control the vast natural resources of the region, especially large quantities of petroleum. Singapore fell on February 15, 1942, and within a month the Japanese military had conquered the entirety of the Netherlands Indies. This great military victory included a devastating defeat for the Allies in the Battle of the Java Sea Java Sea, Battle of the (1942) . The Japanese then turned north and conquered Burma; this gave the Japanese Empire control of 1 million square miles of territory and about 150 million people.

Australia Helps Turn the Tide

With both the Netherlands Indies and most of French Indochina under its control, Japan was now in the position to launch attacks against both India and Australia. India, the “jewel in the crown” of the British colonial system, British Empire;World War II was of particular strategic importance, because if it fell, all of South Asia and the rich oil supplies of the Middle East would be threatened. However, it would be the protection of Australia that would provide the United States with the opportunity to score a much-needed victory against the Japanese navy. In March, 1942, the Japanese high command decided to move against Australia, and it began preparation for military operations against the Solomon Islands World War II (1939-1945)[World War 02];Solomon Islands campaign and the air base at Port Moresby on the island of New Guinea. The Japanese navy planned to use the air base to bomb the coastal defenses of Australia and to control the airspace over the Coral Sea, which would be used as the avenue of advance in an invasion of Australia. On May 4, 1942, a U.S. carrier force intercepted a Japanese naval contingent in the Coral Sea Coral Sea, Battle of the (1942) that was positioning itself to strike the air base at Port Moresby. A ferocious battle ensued, and the United States lost the carrier Lexington; Lexington (ship) however, in the end, the United States put two Japanese carriers out of commission and Japan’s advance toward Australia was halted.

The Battle of Midway

The Battle of the Coral Sea convinced the Japanese high command that the remaining American carrier force had to be defeated. Once again, Admiral Yamamoto prepared to engage the U.S. Navy at Midway Midway, Battle of (1942) in a decisive battle intended to finish the task left uncompleted at Pearl Harbor, giving the Japanese control of the Pacific region. This time, the American forces, led by Admiral Chester W. Nimitz, made good use of their military intelligence, and the U.S. Navy scored an impressive victory, sinking four Japanese carriers. Just as important, many of Japan’s best carrier pilots were killed during this campaign, and their deaths hurt Japan’s ability to make war as aggressively as it had done in the past. The Battle of Midway was a turning point in the war in the Pacific, not only because it punished the Japanese navy but also because it helped engender a belief among the Allies that Japan would eventually be defeated.

The “Island-Hopping” Campaign

The man who had the most significant impact on the ground war in the Pacific was General Douglas MacArthur. He developed a tactical strategy to deal with the problem that the Japanese army had occupied hundreds of islands across the Pacific and that it would be impossible successfully to engage these forces in every Japanese outpost. MacArthur developed the concept of “island hopping” that pinpointed the most strategically important islands and bypassed the rest of the Japanese forces. The Battle of Guadalcanal Guadalcanal, Battle of (1942-1943) set the stage for MacArthur’s tactical plan and introduced the United States to the bloody battles of attrition that would become commonplace in the Pacific theater. Guadalcanal occupied an important position at the southern tip of the Solomon Islands, a strategically important archipelago east of the Coral Sea. From August, 1942, until February, 1943, U.S. and Japanese forces fought a deadly campaign for control of the island. This campaign marked the first successful Allied invasion in the Pacific and established the reputations of American soldiers as constituting a formidable fighting force and of the U.S. military command as effective at planning and executing major military operations.

U.S. Forces Reach Japan

The two most important land campaigns in the Pacific region were the Battles of Iwo Jima Iwo Jima, Battle of (1945) and Okinawa. A vital part of MacArthur’s plan was to establish air bases close enough to Japan to allow American bombers to strike targets on the Japanese mainland. The capture of the Japanese island of Iwo Jima would place the United States’ B-29 Superfortress bombers within range of many of Japan’s industrial centers. Taking Iwo Jima would also give the U.S. Navy the ability to erect a defensive curtain around the central Pacific region, stretching from Midway and the Hawaiian Islands in the east to the Mariana Islands and Guam to the west. In mid-February, 1945, the United States, under the direction of Admiral Nimitz, launched the invasion of Iwo Jima. Japanese general Tadamichi Kuribayashi had been given the task of defending the island. In the months leading up to the invasion, he had constructed multiple lines of defense centered on an extensive system of caves and tunnels into which he placed artillery units and hundreds of automatic weapons. His plan was to inflict as many casualities as possible on the American forces in hopes that the widespread devastation would slow the American advance toward Japan. After weeks of bloody fighting, the American forces gained complete control of the island on March 26, 1945.

The final assault in the island-hopping campaign was the invasion of Okinawa. Okinawa, Battle of (1945) If the allies were able to secure this final outpost in the Japanese defensive perimeter, they would be able both to bomb Japan at will and eventually to launch an invasion of the mainland. The Japanese military government knew that Okinawa would be the final American target, and the Japanese army, under the leadership of General Mitsuru Ushijima, spent weeks turning Okinawa into a deadly fortress. The Japanese high command stockpiled tanks and artillery and brought in thousands of troops in a final attempt to stop the American military machine. General Simon Bolivar Buckner, Jr., commanded the Unites States’ forces, and after almost three months of brutal fighting, the island fell on June 21, 1945.

The Atomic Bomb

The carnage of Okinawa led many intelligence analysts to predict that an invasion of the Japanese mainland would cost more than a million Allied and three million Japanese causalities. Many historians believe this was one of the major reasons President Harry S. Truman decided to drop an atomic bomb on Hiroshima on August 6, 1945, and another bomb on Nagasaki on August 9. As a result of the devastation inflicted by these two formidable weapons, the Empire of Japan surrendered to General Douglas MacArthur on the battleship Missouri on September 2, 1945.


The United States of America came out of World War II as one of two global military superpowers; the Soviet Union was the other. The United States alone, however, possessed atomic weapons at the end of the war. General MacArthur was given the responsibility of rebuilding Japan, so it could reassume its place among the community of nations. Most historians believe that MacArthur succeeded beyond all expectations. He helped the new Japanese government write a constitution that created a parliamentary democracy with a legislative body known as the Diet. He also helped create a modified capitalist economy that, by the early 1970’s, was the second strongest in the world.

By the early twenty-first century, Japan’s economy made it one of the world’s major powers, albeit one lacking military might. Moreover, its technological resources helped drive the economic development and high-tech industries of most of the world’s industrialized nations. The consistent growth of China as both an economic and a military power, however, had begun seriously to shift the power balance of Asia, and it remained to be seen how Japan—or the United States—would respond to these developments. World War II (1939-1945)[World War 02];Pacific theater

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Beasley, W. G. Japanese Imperialism, 1894-1945. Oxford, England: Clarendon Press, 1987. Excellent overview of the history of modern Japanese imperialism. Maps, index.
  • citation-type="booksimple"

    xlink:type="simple">Edgerton, Robert B. Warriors of the Rising Sun: A History of the Japanese Military. Boulder, Colo.: Westview Press, 1997. Provides a detailed account of the rise and evolution of the Japanese military from the late nineteenth century to the end of World War II. Maps, index.
  • citation-type="booksimple"

    xlink:type="simple">Hoyt, Edwin P. Japan’s War: The Great Pacific Conflict. New York: Da Capo Press, 1989. One of the most respected accounts of the causes and effects of Japanese militarism in East Asia. Maps, index.
  • citation-type="booksimple"

    xlink:type="simple">Lewis, Jonathan, and Ben Steel. Hell in the Pacific: From Pearl Harbor to Hiroshima and Beyond. London: Channel Four, 2001. History of the Pacific war, published to accompany a British television documentary by the same name. Bibiliographic references and index.
  • citation-type="booksimple"

    xlink:type="simple">Rawson, Andy. Victory in the Pacific and the Far East: Rare Photographs from Wartime Archives. Barnsley, South Yorkshire, England: Pen & Sword Military, 2005. Stunning collection of photographs taken in the Pacific theater. Part of the Images of War series.
  • citation-type="booksimple"

    xlink:type="simple">Thobaben, Robert G., ed. For Comrade and Country: Oral Histories of World War II Veterans. Jefferson, N.C.: McFarland, 2003. Collects first-person narratives of both the Pacific and European theaters of the war. Index.

World War II: European Theater

Bombing of Pearl Harbor

Japan Begins Attacks on Southeast Asia

Battle of Guadalcanal

Central Pacific Offensive

First Nuclear Bomb Is Detonated

Atomic Bombs Destroy Hiroshima and Nagasaki

Categories: History Content