The battle plan was almost inconceivable. Including the supporting air power and naval logistics, it was to be the largest military undertaking in world history. The attacking force would be made up of thousands of ships, an air force of many thousands of planes and up to 4.5 million men. If it was successful, it would--at great cost to both men and material--bring an end to the Second World War. Its code name was Downfall, and its objective was the conquest of Japan.

By the middle of 1945, the forces of the United States and its allies had fought their way across the Central and South Pacific to Japan's very doorstep. The Philippines had fallen, as had the islands of Iwo Jima and Okinawa, both of which were considered part of Japan's own national territory.

There was no doubt that Japan was badly wounded. The pitiful remnants of her once-proud Combined Fleet were no longer a coherent fighting force: U.S. submarines prowled her waters and brought shipping to a standstill. B-29s on their daily runs converted more of her cities to ash, and carrier air strikes sent fighters and dive bombers zooming low over the countryside, bludgeoning the nation's transport infrastructure back to the middle ages. American and British battleships shelled coastal cities as far north as Hokkaido with impunity.

But the Japanese government was showing no outward sign of willingness to accept or discuss the demand for unconditional surrender. On June 28, Radio Tokyo broadcast: "The sooner the enemy comes, the better for us, for our battle array is complete." The battles of Saipan and Okinawa, in which thousands of civilians had died in the combat crossfire, by their own hand, or with the "assistance" of their uniformed countrymen, had been held up as examples of how the country's martial spirit extended to all its citizens.

While some low-flying American pilots had, in fact, reported sightings of white flags displayed in rural villages, which might have reflected at least a local popular sentiment contrary to that of the Decree, a far more telling fact was that, during the entire length of the war in the Pacific, no organized Japanese military unit of any size had ever surrendered. Still scattered across its disintegrating empire were well over four million men under arms, with about 1,900,000, well-supplied with ammunition, on home soil. A mobilization of over 13 million men--those hitherto considered too old or too young for military service--was underway.

The battle for Okinawa had reinforced the belief that Japan would refuse to surrender. In the battle, which lasted from the April 1 landing until its "official" conclusion on July 2, three Japanese army divisions, with no hope of victory, reinforcement, escape or survival, had held the invading American troops in savage, yard-by-yard combat, killing 12,252 and wounding 36,631. A further 4,907 U.S. shipboard personnel were killed (and 4,824 wounded), many by suicide attacks, which had become a standard tactic during this campaign.

If at all possible, the U.S. strategic planners wanted to avoid a direct invasion. They had considered intensive bombing and a strangling blockade, but previous results of the strategy were making them think twice. Referring to the devastating March 1945 fire-bomb raid on Tokyo [see Tokyo Journal, March 1995] U.S. Army Chief of Staff George C. Marshall commented, "We had 100,000 people killed in Tokyo in one night and it had seemingly no effect whatsoever." The planners began to look at bombing as part of a whole that must include an invasion. On April 3, 1945, a directive from the U.S. Joint Chiefs of Staff ordered the two Pacific commanders, General of the Army Douglas MacArthur and Fleet Admiral Chester Nimitz, to begin joint planning for landings on Japan's home islands.

Downfall was conceived as a two-part strategy. The first would be Operation Olympic, an invasion of southern Kyushu scheduled for November 1, 1945. The second, Operation Coronet, would be a direct assault on Tokyo, Japan's industrial and government heart, set for March 1, 1946.

What the planners did not know at the time was the U.S. development of a secret weapon that would end the war--the atomic bomb. But what if the bombs were not used? What if, even facing the massive attack and almost certain annihilation, the Japanese government did refuse to surrender unconditionally? What if, even in the face of debilitating casualties and the possibility of losing the support of the public back home, the U.S. did decide to go through with the entire invasion scenario?

Operation Olympic was to be similar to the invasion of Okinawa, but on a much larger scale. Kyushu was chosen for its Kagoshima Bay, which could harbor the huge fleet that would later move to invade Honshu. Moreover, 20 military airfields were scattered across the southern part of the island. These would be improved and enlarged to accommodate the U.S. air groups (a total of well over 3000 aircraft) that would move in to provide land-based air cover.

The north and south of Kyushu were connected by road and rail lines that ran along the east and west coasts of the island. Only small local trails snaked through the rugged mountains that bisect the island from northeast to southwest. The objective was to take and hold the southern portion up to the edge of the high terrain, building huge support facilities even before the battle was concluded. Advancing through the mountains or the coastal bottlenecks would, therefore, be unnecessary; instead those barriers would be utilized to hold counterattacks at bay.

Nine divisions were to land simultaneously on three large beachhead areas stretching from the west side of the Satsuma Peninsula to the east-facing beaches of southern Miyazaki. A two-division feint would be directed at Shikoku to draw Japanese forces away from Kyushu, but this force would not, in fact, land. (To give an idea of size, an American division at the time usually counted about 15,000 men; Japanese infantry divisions were larger, about 18,000, but usually more lightly armed, with fewer automatic weapons and lighter artillery.)

The total number of Olympic troops that would cross the beach in the initial operation was to reach 574,000. The U.S. Navy's Fifth Fleet would support the landings with a total of 1831 ships--not counting minesweepers and other auxiliaries--and 1100 carrier-borne aircraft. Meanwhile, the 130 warships and 1600 aircraft of the Third Fleet would savage the east coast of Japan from the Bungo Strait up to Hokkaido and the Kuriles, to sever all transport and communication in and out of Kyushu. Land-based aircraft from the Marianas and Okinawa would continue to pound industry and the cities, with additional mass strikes at targets on the China coast, Korea and, of course, the defenses of Kyushu. If all went well, the huge air and naval bases would be in full operation between 120 and 135 days after the landing.

The assault was foreseen by the defenders. In a January 19, 1945 report to Emperor Hirohito on the preparations for Operation Ketsu-Go, the defense of the home islands, the Imperial General Staff warned of a "final assault on the Homeland in the fall of 1945 at the earliest." Previous assumptions about peripheral Allied assaults on the China coast, Korea and Cheju Island were discarded, although the U.S. mounted an intense campaign of disinformation called Operation Pastel. Major Hori Eizo, a young intelligence officer, correctly deduced the landing areas and the approximate time of the invasion.

Even with the almost 600,000 troops available, it would still be crucial to decide exactly where and how to meet the invaders. A strong defense could begin at the waterline, but that would leave no reserves. If the invaders were allowed to gain a strong beachhead, they might well prove unstoppable even when reserves were thrown into the fight. It was a hard decision, made all the more difficult because both strategies had already been tried at Iwo Jima and Okinawa, respectively, and both had failed. Eventually, a consensus was reached, and forces were deployed for a "water's edge" stand-and-die defense, while other "maneuver" units were to stay in reserve.

The mission of both troops was to bleed the invaders white; they would force a close-range, point-blank melee so ferocious and confusing that the advantages of U.S. mobility and firepower could be nullified. By holding the attackers in such a death clutch, the Japanese leadership hoped that the massive casualties would force the Allies to seek a negotiated peace and abandon their insistence on unconditional surrender.

Even more than in the battle for Okinawa, the Special Attack units were to play a major part in the defense of Kyushu. By X-Day, about 10,500 aircraft--ranging from first-line fighters and attack bombers down to wood-and-wire biplane trainers--would be modified for the Special Attack role; but how many could be within range of the landing fleet was an open question. With no tankers to bring oil from the East Indies, the Japanese were having to distill fuel from pine-tree roots to supplement their dwindling hoard. Special one-way suicide aircraft were in production; the navy was working on advanced jet-powered models of its MXY7 Oka manned flying bomb and the Army had production of the Ki-115 Tsurugi, a cheap, no-frills suicide plane. The pilots were given only about 12 hours of instruction, the minimum needed to get aloft and dive into a target.

At water-level, both the Army and the Navy had Special Attack Shinyo suicide boats; 1280 were expected to be available by the fall of 1945. Both midget submarines and manned torpedoes were being readied in large numbers, and a 4000-man corps of expendable Fukuryu divers was in training. They were to be equipped with a primitive scuba-type apparatus and an explosive charge on a pole to be detonated against the hull of a landing craft or support vessel passing overhead. Navy intelligence estimated that the U.S. landing would require about 2000 vessels, but intense attacks would be made especially against troop transports, hopefully inflicting a loss equivalent to two entire divisions. Their estimates saw Special Attack aircraft destroying 21 U.S. vessels, while midget submarines, manned torpedoes and suicide boats were expected to account for another 270. "The total strength of the Army and Navy," stated a July 13 order from the Imperial General Staff, "will annihilate the U.S. forces . . . in the initial stage of their operations to invade the Homeland."

Meanwhile, the civilian population was being hit with a constant and intense stream of propaganda: "100 million die together" was a major theme. The Third General Mobilization during June and July of 1945 had loosely organized much of the populace into Volunteer Home Defense Units. The People's Handbook of Resistance Combat stated the mission clearly: "One hundred million of us, as the Tokko (Special Attack), must exterminate the enemy to protect our native soil and maintain our eternal Empire."

Some were trained to become nikudan (flesh bullets) and throw themselves against attacking personnel and vehicles with live artillery rounds or mines. These units were to be armed with makeshift armaments, including hunting rifles and shotguns, Molotov cocktails, firemen's tools, farm implements, martial arts training weapons, baseball bats and thrusting lances cut from staves of green bamboo. In June of 1945, hand grenades were issued to the public, although the purpose was for mass suicide rather than defense. In mid-July, the Blind Veterans' Volunteer Corps was organized.

In the U.S. Navy's calculation of probable shipboard casualties, the worst was expected: the Okinawa figures were increased by a factor of 10, with almost 50,000 expected to be killed and about the same wounded. On land, the Army and Marines were realistically expected to suffer some 98,000 dead and 295,000 wounded. These figures were arrived at by the planners of the Kyushu assault, especially medical and supply personnel who had seen combat in the Philippines and Okinawa. The U.S. Army's Philadelphia Quartermaster Depot ordered 370,000 Order of the Purple Heart medals to award those killed or wounded in combat, while a radically more optimistic set of figures--40,000 killed and 150,000 wounded for both Olympic and Coronet--was prepared by higher level planners and had been presented to the Joint Chiefs of Staff and President Truman.

These latest figures had a political taint about them, especially since Gen. MacArthur had actively cultivated an aura of being able to win battles with minimum loss of life compared with the brutal, bloody and costly Marine Corps assaults. Still, it was highly probable that Kyushu would be the bloodiest assault in history. Until Coronet, that is.

On a typical early spring weekday, the beaches of Shonan, Kanagawa Prefecture are much as they were half a century ago: low-angled, their shell-flecked gray-brown sand sloping gently down to meet the foamy wash of the surf. Flocks of gulls and skuas rest and preen and fidget on the sand. Just inland from the strand, what was once rice paddies and clusters of farmers' and fishermens' houses, separated by sandy paths, swaths of beach grass and the occasional grove of pines, has been overwhelmed by the angular concrete of Japan's contemporary suburban sprawl. Save for the roar from passing cars and trucks, the beach itself is peaceful. But 50 years ago, this beach, along with Kujukurihama in Chiba Prefecture, was marked for the climactic amphibious assault of World War II.

The attack on Tokyo was to open with 180 days of continuous bombardment. For six months, the Kanto skies would be thick with droning swarms of giant B-29s and B-32s, carrier planes and Kyushu-based fighters and bombers. There would be JB-2 "jet bombs," a U.S. version of the German V-1. In order to strip away concealing vegetation, clouds of the defoliant chemical 2,4 dichlorophenoxyacetic acid--called VKA (for vegetable killer acid)--would be sprayed on the landscape for a distance of five to seven kilometers inland of the beaches. It was also to be cast at large on the Kanto Plain rice crop, intended to wither and kill at least 30 percent of the year's harvest.

The first American troops were to come ashore on Y-Day, March 1, 1946: two Army divisions in the center of the Kujukurihama beaches, while two Marine divisions would land near Iioka at their northeast end. Moving inland, the Marines would turn right to the Tone River and the town of Choshi at its mouth. While the left flank would strike westward across the base of the Boso Peninsula to secure the east side of Tokyo Bay, the center would push on to the capital itself. The strategy seems simple enough on paper, but it wasn't. To leave the beach area, the invaders would have to conquer the high ground that lies about three- to five-kilometers inland. Defenses were dug in, controlling the approach and passage to the roads to Tokyo. To take out the kind of fortified positions that always seemed to survive the pre-invasion bombardment, the U.S. Army had built a new armored vehicle, the T-92, which married the largest caliber howitzer available (240mm) with a light tank chassis. One round weighed 160kg and could penetrate 1.5 meters of solid concrete at close range.

While the Kujukuri beachhead was ablaze with battle, another invasion force would appear to be preparing to land on the Kashima beaches north of the Tone River. Air attacks, ship movements and false radio traffic would all give the impression of a second assault, but in fact the main body of this force would be moving south. On Y-Day plus 10, a second, even stronger invasion army would come ashore on the Shonan Coast beaches.

Four divisions would establish a beachhead around Oiso, to be followed five days later by two armored divisions redeployed from Europe. Part of this force would pivot to the right to take the Miura Peninsula and the Japanese Navy base at Yokosuka. The left flank, spearheaded by its tanks, would move northward up the fairly level ground of the Sagami River valley toward Kumagaya, to cut off the Tokyo area from reinforcement from the west. This would be the first time for this type of armored combat in the Pacific, and the Japanese Army's armored vehicles and anti-tank weapons were sadly lacking. The standard anti-tank gun could not pierce the U.S. M-4 Sherman tanks' frontal armor and the most the defenders could hope for was to blow off treads, lure the tanks into minefields or overwhelm them with human waves.

The center of the invasion force would close on Tokyo from the west, trapping the city in the jaws of a massive vise. The initial assaults were to be made up of 575,000 men, and by the end of the sixth week after the invasion, MacArthur planned to have half a million troops? in the pincer closing in on Tokyo.

It would likely have been a monster version of the building-by-building destruction of Stalingrad, except that much of Tokyo proper would already have been nothing but ash. (Berlin, which was 80 percent rubble by the time the Soviet Army was at its edges, had held out for weeks.)

The location of the American beachheads had been accurately guessed by the Japanese defense planners, and a defense plan similar to that of Kyushu was under construction. Fixed coastal-defense divisions would hold the invaders in place as "maneuver" divisions would move up to reinforce the defenders. Four divisions and an armor brigade would defend Kujukurihama; three divisions plus two brigades--some of them armored--were to be in place along the Sagami Bay beaches.

To defend Tokyo itself, the Tokyo Defense Army had been organized, although one of its two divisions was specifically tasked to defend the Imperial Palace, where it was to conduct a last-ditch stand like that around the Fuehrerbunker in Berlin. By this time the Imperial Family, the Imperial Household Agency, the Peers' School and the three Sacred Treasures of Japan would have been spirited away to the huge underground Imperial complex at Matsushiro, in Nagano Prefecture, where 11,000 Korean slave laborers had carved a mammoth warren of tunnels and galleries inside Mt. Maizuru. About his mission, Lt. Gen. Jo Iimura commented that Tokyo's defense would be "based more on spiritual demands than strategic necessity."

Counting all forces--including naval personnel turned into infantry--Japan was able to muster about 370,000. The last of the naval power would have been spent against Olympic and what remained could not have mounted the scale of threat that would have met the invasion fleet off Kyushu. Few aircraft would have remained nor would have had enough fuel to fly, and U.S. planes would have held unchallenged mastery of the sky.

Expecting dire casualty figures from the Coronet operation, MacArthur had been pressured by Washington to accept Allied troops in the invasion, but in a mix of logistical realism and imperious chauvinism, he declined. The French had offered tactical air units and British, Australian, New Zealand, Canadian and Indian troops had been offered. They were turned down, on the grounds that the supply system would be burdened to its limits and would not be able to meet needs for other items.

Naval cooperation was a different story, however. Though the British aircraft carriers suffered from lack of range, their steel decks made them far more resistant to suicide attacks than the wooden-decked American carriers. In a gesture of solidarity, MacArthur decided that his command post for the Coronet invasion would be aboard an Australian Navy cruiser. But that--along with Royal Navy groups supporting the invasion fleet--was to be the extent of Commonwealth participation until well after the campaign was underway.

It is likely that the Soviet Army would have moved on to Hokkaido and northern Honshu at least by the time of Olympic, if not earlier, in order not to get caught by the frigid winter weather. With the majority of the homeland troops in the west of Japan or in the Kanto Plain area, the Soviets could have moved quickly south by leapfrogging parachute and amphibious assaults with their infantry and armor advances. By spring 1946, they might well have been within striking distance of Tokyo from the north, and would surely have wanted to have their hand in the fall of the capital.

The defending planners did not foresee two full landings. Most felt that anything besides the Kujukurihama asault would be a diversion, and the coastal defense was structured accordingly. Col. Hiroshi Fuwa, the operations chief responsible for the overall Kanto Plain defense explained with what sounds like desperate optimism: "Judging the enemy's main landing was extremely difficult. . . . Our plan was to select the decisive battle plan on our own." Lt. Gen. Iimura of the Tokyo Defense Army didn't agree. He guessed--more correctly, that the most immediate threat to Tokyo would come from the west, from the beaches of Sagami Bay. He planned to deploy his troops facing in that direction, exactly opposite what the 12th Area Army commanders had decided to do.

The flat lowlands just inland from both assault beaches were major food-producing areas, so the government decided the fields would be worked until the last possible moment. Even if the landings seemed imminent, the adult population was not to be evacuated. Once the invaders were ashore, the civilians were ostensibly to join and support the defending troops, though Lt. Gen. Toshiro Kawabe of the Imperial General Staff saw a limited role for civilians in this fight for the heartland. "We planned to use a small, select number for supporting intelligence and guerrilla operations, but we felt it would not be practical to use all civilians in combat."

If they were not to be evacuated nor used in combat, what role were the civilians to play? In Saipan and Okinawa Japanese civilians caught in battle areas had been pressed into jiketsu, literally, "self-decision," a euphemism for group suicide. Perhaps the military was planning to defend only itself and the real estate it occupied. If the civilians were in the way, they would be expendable.

It was a decision, of course, that never had to be made. The attack did not take place, and both Kyushu, the site of Olympic, and Tokyo, the target of Coronet, were spared the ravages of what might have been history's most ferocious battles. What the planners had envisioned as leading to the end of the war by 1946 was suddenly deemed unnecessary by the atomic bombings of Hiroshima and Nagasaki a year and a half earlier.

When MacArthur alighted from his plane onto the tarmac of the Atsugi Air Base on the outskirts of Tokyo soon after Japanese capitulation, it meant the scrapping of Downfall and the top secret plans that outlined the schedule of attack. All the planning that had been focused on the destruction of Tokyo was discarded. The strategies of war, with their top secret markings, were filed away in the National Archives in Washington, D.C.

"You Can Cook Them with Gas!" opined the Chicago Tribune on March 11, 1945, urging the U.S. military on to fiercer strategies. It was a sample of the public--and official--reaction to the increasing casualty rates in the island war against Japan. The planners, civilian and military, were becoming worried about retaining the support of the general public now that the war in Europe was over. A long, bitter campaign might turn the war-weary Americans against the campaign. Something would have to be done, and new or unused weapons appeared to be the most effective bet. Poison gas had not been used by the Allies, for fear that the Nazis might adopt the tactic in retalitaion and devastate Europe. The Japanese, however, had used gas in China and this had been reported to the president and the Joint Chiefs of Staff as early as 1942; this could be used as a pretext for the use of gas in the Pacific.

On May 29, 1945, Gen. George Marshall commented: "The character of the weapon was no less human than phosphorus and flame throwers and need not be used against dense populations or civilians--merely against those last pockets of resistance which had to be wiped out but had no other military significance." (A method which had wiped out many civilians in Okinawa who had been mixed up with the die-hard remnants of the Army.)

By the spring of 1945, the U.S. had prepared over five million chemical artillery shells, one million bombs, 100,000 aerial spray tanks and 43,000 land mines--with two million unfilled mine casings ready. The Japanese had 10,000 tons of toxic agents, most produced at a special dedicated facility on the island of Okunoshima in the Inland Sea. Had the battle for Kyushu and Tokyo been as savage as everyone expected, it is highly likely that these weapons would have been used.

For Marshall and other planners the atomic bomb was another element in the effort to defeat Japan. "We knew that the Japanese were determined and fanatical," he wrote, "So we thought the bomb would be a wonderful weapon as a protection and preparation for landings." On July 30, 1945, Maj. Gen. Leslie Groves, director of the Manhattan Project, issued a Top Secret memo to that effect, adding, "Dropped on enemy lines [the bomb could] wipe out his resistance over an area 2000 feet in diameter, to paralyze it over an area a mile in diameter, and to impede it seriously over an area five miles in diameter." The memo went on to explain that friendly troops would have to be at least six miles from the site, but if the bomb were exploded at 1800 feet, troops could move immediately through the area, on foot if necessary. No one had any idea of what radiation could do.

Rear Admiral Richard Conolly, one of the senior planners for Operation Olympic, commented after the Hiroshima attack that he would want "six of these things . . . to put one on either side of each landing, before the troops landed." Marshall saw as many as nine being used in that assault: two behind each of the three beachhead areas, with an additional three to be used on areas of potent resistance or on incoming reserves.

One of the Manhattan Project senior officers, Brig. Gen. Kenneth Nichols indicated that for Operation Olympic, "We might supply 15 atomic bombs to support the troops." With a total production of over 30 atomic bombs by March 1946, that would leave over 20 for possible use against the Kanto Plain and other troublesome areas of Japan. The bombs were in fact used against two cities. Had Japan not surrendered, it is difficult to find any reason, military or moral, that might have deterred the U.S. from making fuller use of them in an effort to accelerate Japan's capitulation.

And on Japan's side? On April 25, 1945, a German U-234 submarine departed Kiel with a high-priority technical cargo. It carried drums of mercury--which was in critically short supply in Japan--special fuses, state-of-the-art antiaircraft shells, plans and parts for rocket and jet engines and 10 drums--560kg--of uranium oxide.

When Germany fell that spring, the submarine was rounding the Cape of Good Hope. The Germans surrendered their cargo, but not before allowing the two Japanese officers on board the chance to commit suicide. The submarine was towed to Portsmouth, New Hampshire, but the uranium cargo was kept a secret. Perhaps in the end, some of the cargo eventually did make it to Japan. If the uranium was diverted to the Manhattan Project, some of it might have been included in the Hiroshima bomb.

The Physics Research Institute of Tokyo Imperial University was involved in active, but small-scale nuclear research. The facility was mostly destroyed in a B-29 raid in Apirl, but research continued at other locations, some of it sponsored by the Navy. When news arrived of the destruction of Hiroshima, director Yoshio Nishina was ordered by War Minister Anami to inspect the damage, where he was able to correctly identify the explosion as that of a uranium weapon. After the war, U.S. forces dismantled five cyclotrons and sank the remains in Tokyo Bay.

"We had 100,000 people killed in Tokyo in one night and it had seemingly no effect whatsoever."

--U.S. Army Chief of Staff George C. Marshall

"One hundred million of us must exterminate the enemy to protect our native soil and maintain our eternal Empire."

--The People's Handbook of Resistance Combat