A Japanese soldier trains women to defend the homeland with bamboo spears in 1945. Bushido, or "the way of the warrior," was a code deeply ingrained not only in the military but also in Japan's citizenry. Imperial Japanese Army
Photo Caption & Credits

Japan’s Last Ditch Force

June 1, 2020

In the summer of 1945, the Japanese had almost seven million troops remaining and were not nearly ready to quit.

The Allied strategy in World War II was to win first against Germany and until then to treat the Pacific as a secondary theater. VE Day (Victory in Europe Day), May 8, 1945, marked the victory in Europe. The primary effort shifted to the Pacific, where the war with Japan continued with escalating ferocity.

The Battle of Okinawa was still in progress on VE Day. By the time it was over, 104,520 had been killed in action with total casualties reaching 165,0000 (US 46,000; Japan 119,000).

The next step was subjugation of the Japanese home islands, a far bigger undertaking than Okinawa and with casualties on a higher scale. Japan had a military force of about 7 million remaining and was not nearly ready to quit. 

The Japanese could not possibly win, but they might be able to delay the end of the war into the fall of 1946. If the Americans found the rising casualties intolerable, they might settle for terms less than unconditional surrender.

If we are prepared to sacrifice 20 million Japanese lives, victory will be ours!

—Adm. Takijiro Onishi, vice chief Japanese naval operations

Operation Downfall, the pending U.S. invasion of the Japanese islands, was planned in two phases. It would begin with Operation Olympic on Nov. 1, 1945, an amphibious operation a third larger than the D-Day landing in Europe. 

Once Olympic captured the southernmost island of Kyushu, it would be followed March 1, 1946, by Operation Coronet against the main Japanese island of Honshu. About 2 million U.S. troops were projected to participate in Operation Downfall.

It is unknown how the invasion would have turned out. Japan surrendered on Aug. 15, after the atomic bombs were dropped on Hiroshima and Nagasaki.

 In the postwar period, revisionist historians—eager to prove that it had not been necessary to use the atomic bombs—claimed the war would not have lasted that much longer, and that defeating Japan would not have been that difficult. According to Gar Alperovitz, a leading revisionist, “Japan was on the verge of surrender.”

The revisionists like to quote the U.S. Strategic Bombing Survey (USSBS), which said Japan would “in all probability” have surrendered by November 1945, and “certainly” prior to Dec. 31. This conclusion, which the USSBS study team reached before leaving for Japan to gather information, has been debunked. There is little support for any such theory, either in the survey findings or in the evidence presented by surviving Japanese leaders.

In 1995, egged on by his advisers, the director of the Smithsonian’s Air and Space Museum altered the plan for an exhibit on the dropping of the atomic bomb, marking down from 250,000 to 63,000 the probable U.S. death total from an invasion of Japan. He aroused the wrath of Congress and the exhibition was canceled. 

The revisionists have not given up on arguing their theme. They have also been able to persuade many in the academic world and in the news media to join them in ignoring a mountain of relevant information from 1945.

Closing in on Japan

Acquisition of air bases in the Marianas in late 1944 sealed the military outcome of the war. From there, U.S. B-29 bombers could reach Tokyo and all important targets in Japan. Night after night, the B-29s rained firebombs and high explosives on the wood and paper architecture of Japan.

An attack on Tokyo on March 9, 1945, destroyed 16 square miles of the city and killed 83,793. By the middle of 1945, 50.8 percent of Tokyo had been destroyed, along with 57.6 percent of Yokohama, and 55.7 percent of Kobe.

The Japanese navy was gutted. Most of the Japanese shipping fleet had been destroyed, and maritime activity was severely constrained by a blockade and mines.  Conventional air power was greatly reduced, but there were thousands of kamikaze aircraft and plenty of pilots to fly them on suicide missions. Japan hung on with great tenacity. The army still had 4.9 million troops and was the strong hand in running Japan.

A USAAF B-29 drops incendiary bombs on Osaka, Japan, during a June 1, 1945, mission. The firebombs and high explosives devastated the wood and paper architecture of Japan. USAF

On a visit to Guam in June 1945, Gen. Hap Arnold, commander of the Army Air Forces, expressed his belief that the B-29 campaign would “enable our infantrymen to walk ashore on Japan with their rifles slung.” Arnold did not have the latest information on Japanese strength, and the Japanese did not share his assessment of their position.

There was also some belief that the B-29s were running out of targets. However—and pointed out by the USSBS, no less—the Japanese railroad system had not yet been subjected to substantial attack and trains were running through Hiroshima 48 hours after the dropping of the atomic bomb. Major armament plants at various locations were producing the regular output of military weapons and equipment.

Bushido Nation

What made Japan’s determination to keep fighting credible was the code of Bushido, “the way of the warrior,” which was deeply ingrained, not only in the armed forces but also in the nation at large.

Surrender under any circumstances was dishonorable. Suicide was expected of commanders who had been defeated in battle. Soldiers who surrendered were not deemed worthy of regard or respect.

On Kwajalein, the fatality rate for the Japanese force was 98.4 percent. On Saipan, almost 30,000—97 percent of the garrison—fought to the death. Of 23,000 Japanese troops on Iwo Jima, only 216 surrendered. On Okinawa, 92,0000—80 percent of the total Japanese force—was killed in action. During the entire Pacific War, only one organized Japanese unit ever surrendered: a 23-man “independent mixed battalion” in New Guinea in May 1945.

Adm. Takijiro Onishi, vice chief, Naval General Staff, was not alone in the astounding proposition that, “If we are prepared to sacrifice 20 million Japanese lives in a special attack effort, victory will be ours!” 

Between them, the army and navy could scrape together 10,700 aircraft from all corners of the war front and adapted about 7,500 of them for kamikaze suicide missions, which began in the Philippines in 1944. They sank 33 U.S. ships, damaged 4,900, and claimed almost 10,000 US casualties. In 1945, the Japanese had a million barrels of aviation fuel stored in the home islands, a seven-month supply.

In June 1945, Japan established the “National Volunteer Combat Force,” a civilian paramilitary corps. All males age 15-60 and females 17-40 were required to join. They received training from the army on whatever weapons were available, notably bamboo spears and hand grenades. They were expected to strap explosives to their bodies and throw themselves under advancing U.S. tanks. About 28 million Japanese were subject to conscription under this program.

Japan’s Remaining Forces

The combination of Japanese military assets in 1945 was not a force to be brushed aside or easily neutralized. 

On the day of surrender, the Imperial Japanese forces officially numbered 6,983,000 troops—a hard figure, not an estimate. They were spread in a great arc from Manchuria to the Solomons and the Southwest Pacific, but 3,532,000 of them were based in the Japanese home islands.

Four million civil servants, declared by the War Minister to be on call for military duties.

U.S. Marine 1st Lt. Hart Spiegal tries to communicate with two very young Japanese “soldiers” captured during the Battle of Okinawa on June 17, 1945. DOD

Millions of civilians, armed with bamboo spears and primitive weapons, organized into paramilitary units under army direction.

7,500 kamikaze aircraft, dwindling toward 5,000 through attrition, which was the inevitable result of the suicide strategy.

Almost 700 pieces of seacoast artillery, most of it on Honshu and Kyushu.

Naval coastal defenses: 38 surviving fleet submarines and 19 destroyers, plus suicide boats and midget submarines to attack US troop transports before they reached the invasion beaches. 

The Japanese navy was down but not out. On July 26, the heavy cruiser USS Indianapolis delivered the first atomic bomb to Tinian, then departed for the Philippines to train for the coming invasion. Three days out of Tinian, Indianapolis was torpedoed and sunk by a Japanese submarine. 

Numbers in Motion

In the spring of 1945 public pressure was growing to begin demobilization and discharge of military members. On May 10, two days after VE Day, the War Department announced a point system under which veterans would be returned to civilian life. Credit was given for length of service, combat experience, awards and decorations received, and parenthood of young children.

The first, long-serving troops arrived home from Europe in August, but many others were transferred to the Pacific Theater instead.

 “Fifteen of the divisions in Europe were to augment the 21 Army and six Marine divisions already in the Pacific to fulfill the requirements of Downfall,” said historian Richard B. Frank. “No fewer than 63 air groups likewise were to migrate to the Pacific.”

Meanwhile, Selective Service draft calls to provide the additional forces necessary were running at 100,000 a month. Concurrently, invasion planners discovered that imperial forces in the Japanese islands were increasing faster than anticipated. Between January and June, Japanese strength in the homeland doubled—from 980,000 to 1,865,000. 

The United States had broken the Japanese codes. “Magic” was intelligence from intercepted diplomatic communications, and “Ultra” intelligence was from Japanese army and navy messages.

The Ultra report in August estimated 625,000 troops on Kyushu. That was almost double the Ultra estimate in June of 350,000, but it was far short of actuality. U.S. officials would not learn until after the war that the number of Japanese troops on Kyushu had been 900,000.


In April 1945, Gen. Douglas MacArthur was named Commander in Chief of U.S. Army Forces in the Pacific and designated to lead the invasion of Japan, code- named Operation Downfall. The Operation Olympic phase was to begin Nov. 1 with the objective of seizing the lower third of Kyushu, southernmost of the Japanese home islands. The heart of it would be an amphibious assault operation by nine divisions, compared with six divisions employed in the D-Day landing in Normandy the year before.

The initial expectation was that the nine U.S. divisions would be opposed by three Japanese divisions. That three-to-one ratio satisfied the standard military principle that an offensive force should be significantly larger than the defense force it intends to attack. Even with the updated Ultra estimates in August, the plan for Olympic was not fully adjusted for the 14 Japanese combat divisions in place on Kyushu.

Operation Downfall
The invasion of Japan was planned in two phases. It would begin with Operation Olympic on Nov. 1, 1945, an amphibious operation a third larger than the D-Day landing in Europe. Mike Tsukamoto/staff

The US projection of forces in May forecast 766,700 troops to take part in Olympic, with another 1,026.000 for Operation Coronet aimed at Honshu in March 1946: a total of 1,792,700 committed for the combined operation. About 7,000 U.S. aircraft were assigned to Olympic in what MacArthur called “one of the heaviest neutralization bombardments by naval and air forces ever carried out in the Pacific.” 

Operation Coronet, taking advantage of staging bases on Kyushu, would punch directly into central Honshu, striking for Tokyo and the Kanto Plain. For that, the Japanese would pull out all the stops and throw everything they had left into a desperate defense. 

Even so, it was not an automatic assumption that Olympic and Coronet would be the end of it. MacArthur’s war plan said that, operations would continue as necessary to eliminate “organized resistance.” 

Casualty Estimates

President Harry S. Truman was ridiculed by revisionists for saying after the war that Gen. George Marshall, the Army Chief of Staff, had told him the invasion “would cost at minimum one quarter of a million casualties, and might cost as many as a million, on the American side alone.” 

The revisionists said there was no basis for such numbers. Such a statement was uncharacteristic of Marshall. Truman may have been embellishing, but the numbers are not nearly as preposterous as often alleged.

On at least two occasions, Joint Staff planners made estimates in that range. Using casualty rates from fighting on Saipan as a basis, the planners said that “it might cost half a million lives and many times that in wounded” to take the Japanese home islands. An April 1945 projection set the total casualties probable for the first 90 days of Operations Olympic and Coronet at 1,202,005.

In June 1945, MacArthur gave Marshall his estimate of about 110,000 casualties in the first three months of Olympic. After the war, having seen better information on the suicide defense plans and preparations in Japan, MacArthur revised his opinion. “Those bombs that ended the war saved us about 500,000 casualties, “he said. “The Japanese would have sacrificed at least a million.” 

A Japanese A6M Zero Kamikaze pilot hones in on the side of USS Missouri, o ff Okinawa, on April 11, 1945. The attack caused only minor damage, but the psychological toll of the suicidal bombers on Sailors was significant. U.S. Naval History and Heritage Command

Casualty estimating is notoriously uncertain, but the cost would have been high in two amphibious invasions, facing 7 million Japanese regulars and up to 30 million armed civilians and others, fired up with Bushido and fighting from defensive positions in their home territory.


Japan did not respond immediately to the atomic bombs at Hiroshima Aug. 6 and Nagasaki Aug. 9. The invasion was still on.

Marshall had his staff studying an alternative to using atomic bombs in direct support of the invasion force. At least seven more bombs would be available by the end of October. Manhattan Project officials advised Marshall that although lethal radiological effects would reach out 3,500 feet, the ground would be safe to walk on in an hour. 

The Emperor, who had aligned himself with the peace faction, broadcast his rescript of surrender Aug. 15. There was a flurry of revolt within the army, but War Minister Gen Korechika Anami committed ritual suicide. He was opposed to surrender but would not challenge the Emperor. The formal instrument of surrender was signed Sept. 2 aboard the USS Missouri in Tokyo Bay.

Various factors no doubt contributed to the outcome, but revisionist fantasies aside, the key events were the atomic bombs at Hiroshima and Nagasaki.

The atomic cloud over Hiroshima. The photo was taken from the Enola Gay, which had just dropped the nuclear bomb, Aug. 6, 1945. It took a second bomb to force Japan to surrender. 509th Operations Group

Conventional bombing and blockade would have eventually ended the war, but were not likely to have done so any time soon. Bombing by the B-29s would have resumed, and two nights on a par with the Tokyo attack on March 9 would have exceeded the death toll of both atomic bombs.

Meanwhile, Operation Olympic would have gone forward, against an enemy force three times as large as previously estimated. And that would have left the invasion of Honshu and Operation Coronet yet to come.

In the end, Japan would have been defeated, but the price in lives on both sides would have been terrible.