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World War II (1939–1945)

History SparkNotes

Southeast Asia

The Strengthening Alliance

North Africa and the Invasion of Italy

March 8, 1942 Japan takes Rangoon, Burma
July Japan occupies Guadalcanal
August 7 Allies launch offensive on Guadalcanal
November Allies launch offensive in New Guinea
February 9, 1943 Battle of Guadalcanal ends
August 4, 1944 Allied forces take Myitkyina, Burma
October 20 Battle of Leyte begins
December 31 Battle of Leyte ends
February 19, 1945 Battle of Iwo Jima begins
February 23 U.S. Marines reach Mt. Suribachi
March 26 Iwo Jima declared secure
April 1 Battle of Okinawa begins
May 3 Allies liberate Rangoon
June 21 Battle of Okinawa ends


After the Japanese defeat at Midway in June 1942, the war in the Pacific shifted south, as the Japanese focused on winning complete control of the Solomon Islands. They already had a strong foothold at the north end of the island chain, but occupying the central island, Guadalcanal, was crucial. When the Japanese took Guadalcanal in July 1942, the move threatened Allied shipping throughout the region, and Allied leaders were determined to respond. On August 7, the Allies launched an offensive on Guadalcanal via an amphibious landing of more than 16,000 U.S. Marines onto the island. The landing went relatively smoothly, although the Japanese naval forces sank eight Allied cruisers, two heavy carriers, and fourteen destroyers, killing more than 1,000 men.

Once on the island, the Marines found little resistance at first, since the only Japanese present were construction workers building military facilities. The Americans soon captured an airfield, which they quickly made operational, and all was quiet except for a series of Japanese air raids, which were fought off with the help of U.S. naval air support. By mid-October, however, Japan began streaming troops onto the opposite end of the island, sending wave after wave of soldiers despite terrible losses to American gunfire. The Japanese fought to the last man in virtually every engagement, regardless of the odds, which was shocking and intimidating to the U.S. troops. Attrition and limited supplies eventually resulted in unsustainable losses for the Japanese, but it was a slow process: the Battle of Guadalcanal continued until February 1943, when Japan was forced to abandon the island.

New Guinea

While the Allied campaign in Guadalcanal was going on, the United States and Australia launched a joint offensive on November 16, 1942, into New Guinea, the control of which the Japanese and Allied forces had both been struggling over for many months. As at Guadalcanal, the Japanese displayed a tenacious will to fight for every inch of territory, regardless of the cost in human lives. Although the majority of Japanese forces were driven off the island by January 1943, the Allies were unable to remove them fully, and fighting in New Guinea continued well into 1944.


Japan’s conquests in Southeast Asia during the first half of 1942 extended as far west as Burma. Britain, along with its colonial armies in India, took responsibility for containing this portion of the conflict. The British campaign did not go well, however, and on March 8, 1942, the Burmese port of Rangoon fell to Japan. This setback was a particularly bitter loss for the Allies, as it had been a primary supply point and the site of a crucial base for the British Royal Air Force. By May, the Japanese had driven the Allies back across the Indian border. During the rest of 1942, British-Indian forces launched minor offensives into Burma, but with little success.

It was only in mid-1943, when the Allies organized a new command structure in the region—the Southeast Asia Command—that they made any substantial progress in driving the Japanese back. Under this new command, the British cooperated with the Chinese to advance on the Burmese border, while U.S. and British special operations forces went behind enemy lines to cut communications and create chaos in general. A major focus of the campaign was to capture the town of Myitkyina, which was a principal Japanese communications post. There was a prolonged struggle for the Myitkyina, which finally fell on August 4, 1944. Another goal was to secure the so-called Burma Road, which linked Burma and China but was blocked by Japanese forces. The Burma Road was reopened in January, 1945. Finally, the Allies recaptured Rangoon on May 3, 1945.

The Island Campaigns

Following their success in the Solomon Islands, the Allies fought fiercely throughout 1944 and 1945 to free the many other South Pacific island groups that Japan had seized earlier in the war. Many of these islands had formerly been territories of the United States, Britain, or other Allied countries. The largest of the island groups included the Marshall Islands, the Marianas, the Philippines, and the Ryukyu Islands. The battles took place on land, on the sea, and in the air.

For Japan, it was a nearly continuous series of losses, beginning with the Battle of the Philippine Sea near the Mariana Islands on June 1920, 1944. In this huge sea battle, Japan lost most of its naval air power. Three Japanese aircraft carriers were sunk and more than 300 airplanes destroyed. The ground battles in these campaigns were similar in character to those on Guadalcanal and New Guinea: the fighting involved guerilla-style warfare with very high casualty counts, especially for the Japanese. For example, in the Battle of Leyte, which took place in the Philippines between October 20 and December 31, 1944, the Japanese lost 49,000 soldiers out of a total of 55,000 involved in the conflict. In the same conflict, the United States lost only 3,500 troops.

One by one, the Allies liberated Japanese-controlled islands until the last obstacle between Allied forces and the Japanese mainland were the Ryukyu Islands, which included Okinawa. However, each battle was more intense and more costly than the previous one, which led military commanders to begin rethinking their strategy.

Iwo Jima

A small island off the Japanese coast, Iwo Jima served as an early warning station against Allied bombers en route to attack Japan. As the Allies closed in on Japan, Iwo Jima became an obvious target. Following a heavy bombardment of the island by aircraft and battleships, U.S. Marines began an amphibious assault on February 19, 1945. Over 20,000 Japanese troops were garrisoned on Iwo Jima, and the entire island was honeycombed with underground tunnels and bunkers, especially Mt. Suribachi, which overlooked the southern end of the island.

After U.S. forces came ashore, they surrounded the base of Mt. Suribachi within a single day. Ascending the mountain was another matter entirely, as the Japanese fought from their hidden tunnels and small bunkers on the steep, ash-covered slopes. After a brutal, four-day struggle, U.S. forces reached the peak of Mt. Suribachi on February 23, where an Associated Press photographer took a now world-famous photograph of a group of Marines raising the American flag. Although taking the mountain was a victory in itself, it would be more than a month before U.S. forces secured the entire island. Approximately 20,000 Japanese soldiers—nearly all the forces on the island—were killed. The American death toll was 7,000.


The Battle of Okinawa was the last large-scale battle in the Pacific and the most intense of the island invasions. Unlike Iwo Jima, Okinawa had a large civilian population, which became one of the great tragedies of the battle.

U.S. forces began amphibious landings on April 1, 1945. Japan had more than 100,000 soldiers lying in wait in a series of fortified defensive lines. The Japanese believed that the Allied weakness would be its large fleet of naval vessels anchored offshore. As a result, they planned a massive series of kamikaze attacks on these ships—suicide missions in which Japanese pilots crashed their fuel- and bomb-laden planes into targets—with the goal of destroying the ships or forcing them to abandon their troops on land. However, these kamikaze attacks did not do nearly as much damage as the Japanese had anticipated, and the U.S. fleet was able to remain in place and continue to offer air support to the troops on the ground.

The battle lasted for two and a half months, until June 21, and cost nearly 19,000 American lives. The Japanese losses were even more sobering: more than 100,000 Japanese soldiers were killed, while the civilian death toll was estimated to be 80,000 to 100,000.

Mounting Casualties

As Allied forces retook one by one the territories that Japan had captured earlier in the war, they became alarmed by Japan’s increasingly extreme tactics. At Guadalcanal in August 1942 and in nearly every battle afterward, Japanese forces simply refused to surrender, even when they were clearly losing. This tactic resulted in huge death tolls for the Japanese forces, as well as increased Allied casualties. Each battle became progressively worse in this respect, and by the battles of Iwo Jima and Okinawa in 1945, the Japanese were fighting to nearly the last man. In Okinawa, even many Japanese civilians committed suicide when it became clear that the island was falling to the Americans.

These developments made Allied commanders worry about what it would take to win the war. Although the Allies had a plan in the works to land U.S. ground troops on the Japanese home islands, if the Japanese population chose to fight to the death, as many were speculating, the cost in American lives would be overwhelming. As Allied forces closed in on Japan proper, however, the U.S. Air Force was able to stage extensive bombing raids over Japanese cities, including Tokyo, which gradually began to demonstrate a viable alternative to a ground invasion.

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