“The U.S. military, expecting the resistance of a ‘fanatically hostile population’, were making preparations for between 1.7 and 4 million casualties.”

IT COULD BE called the world’s greatest battle… that never happened.

Operation Downfall, the codename for the U.S.-led mission to capture the Japanese homeland in 1945 and 1946 never did take place. Had the invasion not been preempted by the dropping of the atom bombs on Hiroshima and Nagasaki, almost all agree that the campaign would have stood as the bloodiest chapter of the Second World War, adding as many as 10 million additional dead (both civilian and military) to the war’s already mind-boggling final body count of 50 million.

Downfall was the brainchild of Admiral Chester Nimitz and generals Douglas MacArthur and George Marshall. It was comprised of TWO mammoth amphibious operations. The first phase, dubbed Operation Olympic was planned as a November, 1945 assault on the southernmost Japanese home island of Kyushu.

Phase two, Operation Coronet, was to kick off in March 1946 and would have involved a series of landings on the island of Honshu that were intended to put Allied ground forces within reach of Tokyo.

Olympic

The Olympic plan included 14 army divisions in the initial landings alone, supported by an armada of 400 destroyers, 24 battleships and a staggering 42 aircraft carriers. The invasion force itself would hit 35 landing beaches that ringed the southern third of the island, all codenamed for cars: Buick, Cadillac, Stutz, etc. Overhead, aircraft from the 20th, Fifth, Seventh and 13th air forces would pulverize Japanese airfields, communication lines and troop concentrations, while the guns of the naval forces would demolish coastal defences. Supporting the operation would be a British Commonwealth fleet comprising the entire Pacific arm of the Royal Navy, which included up to 18 aircraft carriers and four battleships.

Once Operation Olympic had secured the southern portion of Kyushu, the stage would be set for the even larger second phase, Coronet.

Coronet

Scheduled for March, 1946 the landings on Honshu would use forces already committed along with significant numbers of fresh troops brought over from Europe. A Commonwealth corps would include units from Australia, Britain and Canada. Aircraft from the RAF’s Bomber Command would also be redeployed from Europe for the final push. All in all, Coronet would dwarf Olympic, using 25 army divisions in the initial assault alone – that’s more than twice the number of divisions committed to the opening of Operation Overlord in 1944.

The Japanese anticipated the objectives of the Allied invasion plans, although the leadership expected the blow to fall in the summer of 1945 immediately after the capture of Okinawa.

Strategy for Defence

The Japanese plan for this final battle was dubbed Ketsugo or “Decisive.”

While nearly four years of war had seen the Japanese fleet decimated, the Emperor’s forces planned to throw their remaining six carriers, four cruisers and one battleship, along with 350 midget submarines, 400 manned torpedoes and 800 suicide speed boats into action against the Allied armada.

On the ground, Japan had a total of 900,000 troops formed into 65 divisions, although it only had weapons and ammunition for between 30 and 40 divisions. Almost all of these would be committed to the defence of Kyushu. Supporting the troops would be a 28-million-strong ad hoc militia army called the Patriotic Citizens Fighting Force. This was made up of all healthy males between the ages of 15 and 60 and women aged 17 to 40. These formations would go into battle almost completely unarmed. Many civilians were issued surplus rifles, antique muskets, bows and even sharpened bamboo pikes.

Japan’s air force would rely heavily on its Kamikaze pilots. More than 10,000 were expected to be used, primarily against troop transport ships.

Worst Case Scenarios

Both sides braced for heavy casualties. The U.S. military, expecting resistance by a “fanatically hostile population,” made preparations for between 1.7 and 4 million casualties with up to 800,000 dead. Between 5 and 10 million Japanese deaths were projected.

The Japanese leadership had no illusions that this final act of resistance would somehow lead to victory, but many in the high command were optimistic that a spirited defence might compel the Allies to negotiate a favourable peace rather than spend the resources and lives in such an epic fight.

Surrender

Fortunately, Downfall never happened. The two atom bombs, dropped nearly four months before the invasion was to begin, brought the war to a swift conclusion. While the attacks on Hiroshima and Nagasaki cost the lives of upwards of 250,000 Japanese civilians, historians agree that a protracted ground campaign would have killed millions.

More Downfall facts:

Here are some remarkable details about Operation Downfall:

The Japanese homeland was going to be bitterly contested. Both side expected the other to use poison gas, yet neither had plans of their own to use chemical weapons.

The U.S. strategy called for the assistance of British and Canadian troops brought in from the European theatre, along with a contingent of Australians. To ensure interoperability, MacArthur insisted that these units be trained in the U.S. in the months leading up to Coronet. Additionally, the Allied divisions would fight under a U.S.-style corps structure and the general wanted them to only use American equipment.

MacArthur rejected the suggestion that a contingent of Indian troops be included in the order of battle, citing the language barrier as the main sticking point.

The Manhattan Project was so secret that few involved in the planning of Downfall initially knew of the atom bombs’ existence. As details of the weapons were revealed in mid-1945, the invasion planners actually anticipated using them to directly support ground combat. In fact, the Pentagon planned for up to seven nukes be available for use in the campaign.

Expecting heavy casualties, the U.S. military ordered the production of half a million Purple Heart citations in 1945. Since the war ended before the invasion, the American military put the medals into storage and has been drawing from the stockpile in every war since then. There are still nearly 100,000 Purple Hearts in the U.S. inventory left over from the production run prior to Downfall.

(Originally published on June 1, 2012)

Like this: Like Loading...