World War II: The War Against Japan

World War II Reference Library. Editor: Barbara C Bigelow, et al., Volume 2: Almanac, UXL, 2000.

By the spring of 1942, Japan had conquered a vast territory. It stretched thousands of miles from the border between Burma (present-day Myanmar) and India east to the Gilbert Islands in the middle of the Pacific Ocean. The Japanese controlled most of the immense island of New Guinea, situated south of the equator near Australia, and small Arctic islands in the Aleutians, off the coast of Alaska. In all these places, battles raged from the time of the Battle of Midway in June 1942 (discussed in Chapter 4) and the final defeat of Japan in August 1945.

The largest Japanese force, by far, was in China, which was the scene of large battles and great human suffering. But for the most part, the Japanese army in China avoided major offensive actions. The Chinese armies—almost all poorly equipped, poorly trained, and poorly led—did the same. Despite pressure from the United States, which provided arms, supplies, and training to the best Chinese troops, the Chinese leaders never seriously threatened the Japanese. The battles fought in China did not decide the outcome of World War II in Asia. Neither did the attempts to retake Burma that cost the lives of many British and Indian troops, as well as their Japanese enemies.

The War in Asia Becomes a Pacific War

Instead, the war against Japan was decided by events in the Pacific, a war fought almost entirely by the United States. In the western Pacific, it involved huge spaces—thousands of miles of open ocean dotted by groups of small islands, including the Gilberts, the Marshalls, the Carolines, and the Marianas. Farther south, nearer Australia, the islands were much larger and the distances between them shorter.

Month after month, from Australia northward and from Hawaii and Midway westward, the Americans pushed back the Japanese. From both directions, U.S. forces advanced slowly toward Japan. Protected by ships and airplanes, the marines and soldiers of the U.S. Army (and, in a few places, Australian soldiers) landed on island after island. After each landing they fought to overcome the Japanese troops, who usually resisted with tremendous determination— sometimes literally to the point of suicide. When the island, or one region of a large island, was secure, with airfields and facilities for warships established, the war would move farther north or west to a new island. Sometimes the next target was hundreds of miles away. Sometimes the Americans bypassed islands still held by the Japanese because the enemy forces there were now isolated and useless. For almost three years, the Americans conquered (or reconquered) one island after another. When the war in Europe ended in the spring of 1945, American forces were in the middle of the largest of these Pacific island battles, on Okinawa—less than 400 miles from Japan itself.

World War II and the Pacific Strategy

Taking one island after another was the basic American strategy for the war against Japan—a Pacific war, where the navy used its power to protect an invasion of an island, usually involving relatively few soldiers. It was not the only way that a war against Japan might have been fought. For example, the Allies (Britain, the United States, and the other countries fighting on their side) could have sent armies to attack the large Japanese force that was stationed in China. Such a war might have been similar to the war in Europe, with large masses of soldiers led by tanks, supported by artillery, and protected by planes.

But a land war in Asia was not a real possibility because the United States had decided that the Allies should concentrate their forces and resources on defeating Nazi Germany first. Only after Germany surrendered would they forcefully pursue the war against Japan. In the meantime, the Allies would prevent Japan from expanding further and, if possible, win back some of Japan’s conquests.

The motive behind the Allied strategy was to prevent an immediate German victory in Europe. At the time the United States entered the war, in December 1941, both Britain and the Soviet Union were in serious danger. German submarines were winning the Battle of the Atlantic, threatening to cut off Britain’s supplies. German leader Adolf Hitler’s armies controlled almost all of Europe and had nearly reached Moscow, the Soviet capital. (These events are described in Chapter 3.) If America had concentrated on defeating Japan, then later it might have found itself facing Germany alone—with the Soviet Union conquered and destroyed by Germany, and with Britain having been forced to make peace.

A Large Navy and a Small Army

The Germany first decision was the driving force behind the way America fought the war against Japan. The Pacific strategy stressed the use of American naval power. Part of the reason for this involved the efficient use of valuable resources. American shipyards were building great warships in increasing numbers. These battleships, cruisers, and aircraft carriers could be spared more easily from Europe and the Atlantic than planes, tanks, and cannons. In the Atlantic, naval power was supreme. Navy ships were needed to protect merchant ships (civilian ships that carry freight) that were bringing food and weapons from the United States to Britain. German submarines were a constant— and serious—threat. Generally, the type of escort ships needed in the Pacific were fast and relatively small. Small aircraft carriers, carrying planes designed for antisubmarine warfare, were useful in the Atlantic. But the great fleet carriers—with their fighters, bombers, and dive bombers—that were so important in the Pacific were far less useful in Europe and the Mediterranean, where air bases on land were usually close by.

Because of the island-hopping strategy chosen for the Pacific war and the huge distances the Americans crossed, the number of warships and planes involved was great. By the end of the war, the American fleet in the Pacific was the largest in the history of warfare. Three thousand planes based on aircraft carriers, and thousands of others based on land, dominated the air. But the actual number of soldiers, sailors, and airmen who fought the battles of the Pacific was small compared with the size of the armies that fought in Europe.

The use of a relatively small number of combat troops was a key factor in the American Pacific strategy. The number of marines or soldiers who landed on a particular island might be fairly large, but only one or two battles were going on at the same time. The great majority of the battles in the Pacific were fought by six American army divisions and four marine divisions (a division is usually around 15,000 men). Although troops from some of the additional nineteen divisions in the area saw some action, the American combat force in the Pacific really amounted to an army of about 150,000 soldiers. The entire Japanese army outside Japan and China was about the same size.

In comparison, millions of soldiers were involved in the European war. In mid-1944, 300 divisions of the Soviet army were fighting the Germans in Russia, while another 70 British and American divisions fought in western Europe. Against them, Germany and its Axis partners in Europe had about 300 divisions.

Another benefit of the Pacific strategy was that it led to quick successes that the American people could read about and celebrate. This was especially important after the Japanese triumphs against the United States at Pearl Harbor and the Philippines, only a few months earlier. The American strategy allowed a comparatively small number of troops to attack an island and win a clear-cut victory. In contrast, it took almost a year after entering the war for American troops to fire a shot against the Germans. (This happened during the North Africa campaign in November 1942, described in Chapter 10.) Each island campaign in the Pacific meant another victory, usually within a short time. This was unlike the long, drawn-out fighting in Europe, where individual battles seemed to be part of a single, endless advance toward Germany.


Historians generally agree that another, related reason for the way the war in the Pacific was fought was the rivalry between the top admirals of the U.S. Navy and the generals of the army. Admiral Ernest King, the chief of staff of the navy, and other leaders were never really happy with the Germany first decision. Throughout the war, Admiral King argued for sending more resources to the Pacific. He knew that his opinion was shared by many Americans, who wanted revenge for Pearl Harbor.

Disputes about resources continued throughout the war. Probably the best-known example concerned the navy’s not being willing to send landing craft to Europe, preferring that the craft be sent to the Pacific instead. Some historians believe the shortage of landing craft was a major factor in delaying the D-Day invasion of France. When the invasion finally came, naval support for the landings was vital—but it was still support for what was really an army operation. The ships, like the soldiers and the air forces, were all under the command of an army general, Dwight D. Eisenhower.

Although these developments occurred later, it was obvious as soon as the United States entered the war that the army would play the major role in Europe. The navy was determined to play that same role in the Pacific. If Germany first meant that the Pacific would not get as many resources as Europe, then at least the navy would run the operation.

The island-hopping strategy that the navy proposed was based on a plan that the navy had drawn up long before the war, in case of a Japanese attack. It involved landings on a series of islands, some of them tiny, located in the Solomon, Gilbert, Marshall, and Mariana Islands. The ground troops that attacked these islands would be under the command of Admiral Chester Nimitz. This force included army troops as well as marines, whom Nimitz preferred to use. (The Marine Corps is part of the Department of the Navy, not the army.) No army general would command any of the navy’s ships. (In the European area, the commanding officer of an area, regardless of whether he were army or navy, controlled all forces in the region.)

The army was not happy with this arrangement. Especially unhappy was General Douglas MacArthur, who had commanded the defense of the Philippines and was now in Australia. The heroism of the American soldiers fighting in the Philippines in the early months of the war had made MacArthur very popular in the United States. (The Japanese attack on the Philippines is described in Chapter 4. MacArthur is described in a box in that chapter as well.) He and the army used his popularity to gain the advantage in disagreements with the navy. As part of a compromise between the army and navy, MacArthur was made commander of the Southwest Pacific, which included Australia, New Guinea, the Dutch East Indies, and the Philippines. Admiral Nimitz soon named Admiral William Halsey to command the South Pacific Area, east of Australia. The rest of the Pacific was under Nimitz’s direct command.

A Double Strategy

The division of command between MacArthur and Nimitz, and between the army and the navy, meant that the American effort against Japan would take two different forms. MacArthur’s soldiers would fight the Japanese on a series of large islands north of Australia. Often the Japanese outnumbered them, but the American forces defeated them anyway, through superior tactics and leadership.

Nimitz and the navy would drive west across the Pacific, attacking a series of small islands with overwhelming naval and air force. In one battle after another, they suffered heavy casualties, but they inflicted much heavier losses on the Japanese defenders.

This double strategy was originally an attempt to satisfy both the American army and navy—specifically MacArthur and Nimitz, both strong-willed men determined to get their way. By splitting the American attack along two routes, it might have made each one too weak to succeed. Instead, the opposite happened. Each of the campaigns was powerful enough to defeat the forces Japan placed in its path. The Japanese could never shift enough military and naval forces to stop one of the American advances without severely weakening their defenses against the other.

The United States Strikes Back: Guadalcanal

In August 1942, only two months after the great American naval victory at Midway (which is described in Chapter 4), Nimitz launched the first American offensive operation of the war. A relatively small force of U.S. Marines landed on the island of Guadalcanal, in the Solomon Islands. The Americans planned the operation very quickly, with little knowledge of the geography or conditions the marines would face. The island had rugged jungle terrain and it was incredibly hot and humid. Tropical diseases, especially malaria, were very common.

Guadalcanal had some military importance because the Americans could use an airfield there as a base for further advances. The Americans and Japanese each thought it would be a short fight, perhaps a week or two. But the battle that developed became much larger than the island’s military value could justify.

The Japanese leaders understood that they could not defeat the United States in a long war because the United States’ industrial power was so much greater. Japan’s hope was that it might make the cost of victory so high—in American lives and in money—that the United States would agree to a compromise peace that would leave Japan in control of much of eastern Asia. (This topic is described in more detail in Chapter 4, in the section titled “Japan’s strategy for the war.”) The key for Japan was to make the war so difficult and so bloody that the American people would stop supporting it.

So the battle of Guadalcanal was the first test of America’s island-hopping strategy, but it was also crucial for Japan’s long-term plans. Each side threw more and more resources into the fight, as winning became increasingly important. At that time, the Japanese army had not yet given up an inch of conquered territory. American ground troops had not been involved in combat anywhere. The Americans were determined to prove that their soldiers could defeat the Japanese; the Japanese wanted to prove the opposite.

So the Japanese rushed reinforcements to Guadalcanal to drive the Americans away. The Japanese thought there were fewer marines than had actually landed and sent too few troops. When these reinforcements could not defeat the U.S. forces, more troops arrived. For a while, Japanese warships brought small numbers of Japanese troops and supplies every night. The Americans called the system the Tokyo Express.

In response, the Americans sent reinforcements of their own. Eventually, army troops joined the exhausted marines. For six months, the two sides fought dozens of small, bloody battles: for the airfield, for high ridges or little streams, and for a few hundred yards of jungle.

A series of five major sea battles also took place as part of the Guadalcanal campaign. In these battles, dozens of ships were lost to the guns and torpedoes of enemy warships and carrier-based planes. The Americans called the water between Guadalcanal and a nearby island Ironbottom Sound because so many ships had been sunk there. In the long run, the result of these battles was that Japan was unable to resupply its troops on the island or defend them from the growing number of American planes and soldiers.

By January 1943, it was clear that the United States would win control of Guadalcanal. Unlike in many later battles, the Japanese leadership in Tokyo decided to withdraw its remaining troops rather than fight to the last man. The Japanese officers on the island obeyed this order, possibly because it was personally approved by the emperor. By early February, the last 13,000 Japanese soldiers boarded warships and escaped from Guadalcanal. Of the 36,000 Japanese troops who fought on the island, 14,000 had been killed and another 9,000 had died of tropical diseases. The dead included hundreds of trained pilots killed in the sea battles. Like the many experienced Japanese pilots who died at Midway, they could not be easily replaced. Almost as many Japanese soldiers had been killed on this single small island as had died conquering Japan’s vast new empire in Asia less than a year earlier.

American casualties were also high, although they were much lower than the Japanese. This was a pattern that would be repeated again and again in the Pacific war. At its height, American strength on Guadalcanal was more than 50,000 men; 1,600 were killed and 4,300 wounded; thousands more developed malaria. The First Marine Division, the first to land on Guadalcanal, was temporarily destroyed as a fighting unit. It had lost 774 dead and nearly 2,000 wounded. More than 5,000 of its men—more than one-third—had become sick with malaria.

Suicide in the Far North

At the time of the Battle of Midway in June 1942, the Japanese had captured islands in the Aleutian chain, which was part of Alaska. The islands were very cold, often battered by storms and high winds, and covered in fog, which meant they were not very useful as air bases. Even so, Admiral Nimitz decided to retake them.

In May 1943, Nimitz sent an army division and powerful naval forces, including battleships, to the island of Attu. The 2,500 Japanese troops on the island, although heavily outnumbered, strongly defended their positions, retreating slowly and inflicting serious losses on the American attackers. But after two weeks of fighting, the Japanese were at the end of their strength. Instead of surrendering, however, the Japanese commander led his troops in a bayonet charge against the Americans. Hundreds of Japanese soldiers then committed suicide rather than be captured. Almost all the Japanese defenders of Attu died; the Americans captured just twenty-eight alive. The Americans—despite having to attack strong defensive positions—lost about a third as many soldiers.

Two months later, Japanese warships evacuated more than 5,000 troops from the Aleutian island of Kiska under cover of fog. The waiting American invasion force of 34,000 men took the island without a fight.

Clearing the Solomons

The most important Japanese military and naval base in the southern Pacific was at Rabaul, on the large island of New Britain. Driving the powerful Japanese forces from Rabaul would be very difficult, but it became the first major goal of the combined American navy and army strategy.

After the victory on Guadalcanal, the navy continued west through the rest of the Solomon Islands. At the end of June 1943, troops landed on New Georgia, and on Vella Lavella in August. They skipped the island of Kolombangara, leaving the 10,000 Japanese troops there in control of the island but unable to play any part in the war because they were surrounded by American troops. This was an example of the island-hopping strategy. In November, a division of marines, soon joined by an army division, landed on Bougainville, at the northwestern end of the Solomons chain. They soon built an airfield and established a powerful defensive position. The 35,000 Japanese troops on the island could not crack this position, and American naval and air power prevented Japanese reinforcements from joining them. The American base on Bougainville was within striking distance of Rabaul.

Closing in On Rabaul: The Fighting in New Guinea

Meanwhile, General MacArthur’s Australian and American troops were fighting on New Guinea, just north of Australia. New Guinea is the second-largest island in the world, about twice the size of France, but with few roads, high mountains, and impassable rain forests. Before the war it was divided between the Dutch, who controlled the western half of the island, and Australia, which controlled the eastern half, including the southeastern quarter, called Papua. Japanese troops occupied the Dutch half as part of their conquest of the Dutch East Indies in early 1942. In May of that year, the Japanese tried to land troops on the southern coast of Papua, near its capital, Port Moresby. From there, they could threaten Australia itself. This attempt led to the Battle of the Coral Sea, the first great naval battle fought between aircraft carriers.

With their fleet driven off in the famous battle, the Japanese instead landed troops on the north shore in July and attempted to attack Port Moresby by crossing the mountains along a single jungle trail—something that MacArthur and his planners had thought was impossible. Australian troops defending the trail were pushed back. In mid-September, the Japanese were only 40 miles from Port Moresby, but they could no longer get enough reinforcements to make up for the men they had lost. By then, the Americans had landed on Guadalcanal. Japanese ships were being used to bring reinforcements and supplies there. Unlike the Allies, the Japanese did not have the resources to attack in New Guinea and Guadalcanal at the same time.

Now MacArthur went on the offensive. The Australians forced the Japanese back to the north shore of Papua. Meanwhile, American troops landed by boat at other points on the north shore. By the end of January 1943, the Allies had cleared Papua of Japanese forces. In six months of fighting, more than 12,000 Japanese soldiers died. The Allies lost almost 4,000 soldiers, more than three-quarters of them Australians. Another 7,500 Allied soldiers were wounded.

In a series of battles over the next eight months, MacArthur’s forces moved farther west along the New Guinea coast. In October 1943, the Allies captured Finschhafen, a port across the strait from New Britain. On the other end of New Britain was the great Japanese base at Rabaul. A month later, with the success of the American operation on Bougainville, the Allies could threaten Rabaul from New Guinea to the south and from Bougainville to the east.

The attack on Rabaul might have been very costly. But the 100,000 Japanese troops on New Britain and New Ireland were now isolated. They had suffered constant American air raids, and many of their planes had been destroyed. American naval strength in the area was far greater than the Japanese. The forces at Rabaul did not have the air or sea power to support Japanese forces elsewhere. There was no American attack on Rabaul. The Japanese forces there could stay until the end of the war.

Nimitz Moves West

Instead, Nimitz and MacArthur moved far beyond Rabaul. In November 1943, Nimitz’s marines landed on the tiny island of Tarawa in the Gilbert Islands. Almost the entire Japanese force of 5,000 soldiers defending the island was killed, refusing to surrender even when further resistance was useless. But the marines lost 1,000 men and 2,000 were wounded.

In February 1944, the advance continued northwest to the Marshall Islands. Early in the month, after a tremendous naval bombardment, marine and army troops captured the island of Kwajalein in four days of fighting. They suffered far fewer casualties than at Tarawa. Within two weeks, American troops landed on Eniwetok, the farthest west of the Marshall Islands, and captured it in a battle that lasted five days. The Americans bypassed all the other islands between Kwajalein and Eniwetok because, without a powerful Japanese navy, the soldiers on those islands presented no threat.

The next target was the Mariana Islands, 1,000 miles across the Pacific from Eniwetok—and within striking distance of the Philippines. The new B-29 long-range bomber, known as the superfortress, could even reach the cities of Japan from the Marianas. The first island the Americans attacked was Saipan, on June 15, 1944. The date shows how great Allied resources were: it was barely a week after the Allies had launched the invasion of northwest Europe, landing hundreds of thousands of soldiers in Normandy in France. (The Normandy invasion is described in Chapter 11.)

Two marine divisions and one army division attacked Saipan, which was defended by 32,000 Japanese. As usual, the Americans had strong naval and air support to protect their landing. The fighting continued for three weeks. At the end, the remaining Japanese troops, running low on ammunition, charged the amazed Americans with bayonets. After that, hundreds committed suicide by jumping off cliffs. The Amercians quickly followed up this bloody victory with much easier ones on Tinian and then on Guam, an American island that Japan had captured in December 1941, immediately after Pearl Harbor.

Meanwhile, in the two-day Battle of the Philippine Sea, American carriers thoroughly defeated a Japanese fleet. The Americans lost 29 planes while shooting down 243 enemy planes—almost two-thirds of the total Japanese strength. The Americans called it the Great Marianas Turkey Shoot. Three Japanese carriers were sunk and one was damaged. The battle confirmed that the United States now had higher-quality planes and better radar than the Japanese. In addition, Japan’s pilots were increasingly inexperienced replacements, not nearly as skilled as the men who had won Japan’s first great victories.

Closing in On the Philippines

While the battles for the Marshalls and Marianas were being fought, MacArthur’s troops continued their advance northwest along the coast of New Guinea, avoiding most of the Japanese troops stationed on the island. In a series of carefully planned operations, large Allied forces landed at points along the coast, usually surprising the Japanese defenders. In each case, the American aim was to capture or build an airstrip and create a strong base that the Japanese could not eliminate. Planes from the new airfield would provide cover for the next operation. By July 1944, American troops had established bases in the extreme northwest corner of the giant island, the area known as Vogelkop (“bird’s head” in Dutch, because of its shape). From here, the next step was the Philippines.