What if the a‑Bomb Had Never Been Invented – and America Invaded Japan in 1945?
In the summer of 1945, U.S. leaders expected one million American soldiers would soon be dead or wounded.
Operation Downfall – the codename for the proposed amphibious invasion of Japan in 1945 – would have made the D‑Day invasion of Normandy look like a cakewalk. The first phase – Operation Olympic, scheduled for November 1945 – called for seizing airfields on the southernmost Japanese island of Kyushu. Those airfields would have provided air cover for Operation Coronet, slated for March 1946, which would landed Allied troops on the main island Honshu, for an assault on Tokyo that hopefully would compel Japan to surrender.
In the end, Japan did surrender on August 15, after atomic weapons had been dropped on Hiroshima and Nagasaki, and the Soviet Union had declared war on Japan. But what if Japan hadn’t surrendered? What if the A‑bomb hadn’t been invented, or Japan chose to fight on regardless, and the Allies had storm Tokyo?
A computer wargame suggests an invasion of Japan would have been a bloodbath.
Even in the summer of 1945, assaulting Japan seemed a grim prospect. American soldiers had suffered a forestate in the bloody invasions of Iwo Jima and Okinawa, where Japanese troops fought to the death rather than surrender. How much more fanatical would have been their defense of the sacred Japanese homeland, including thousands of kamikaze aircraft and boats that would have taken a heavy toll of Allies ships. Pentagon planners warned that that Allied troops – mostly American, but supported by British, Canadian, Australian and New Zealand contingents – could suffer up to one million casualties. Japanese military and civilian casualties would have been far heavier.
But on August 6, 1945, a U.S. B‑29 bomber dropped an atomic bomb on Hiroshima, followed by another A‑bomb on Nagasaki on August 9. To the relief of many Americans and Japanese — including my late father-in-law, a B‑29 bombardier who would have flown air support for Operation Olympic – Japan surrendered a few days later.
For decades, controversy has surrounded the decision to drop The Bomb. The traditional narrative has been that the atomic bombs spurred Japan to surrender, and spared millions of American and Japanese. Revisionist historians argue that the A‑bomb was unnecessary and even immoral: Japan, already starving from the Allied naval and air blockade, would have surrendered anyway once the Soviet Union declared war on Japan. Or, that the million-casualty estimate was exaggerated (for a good summary of the arguments pro and con, see this article by historian Alex Wellerstein).
Whichever argument is right – or more likely both arguments are right — historians have tended to focus on high-level questions of war and peace, diplomacy and weapons of mass destruction. But what would an actual Allied invasion of Japan have looked like?
A clue can be found in Japan ’45, from John Tiller Software, a hobby wargame that depicts Operation Olympic (a sequel, Japan ’46, covers Operation Coronet). Japan ’45 is a battalion-level simulation involving thousands of U.S. Army and Marine, Japanese, British and French units maneuvering over a 2‑D map of Kyushu.
At first glance, the Allies appear to be an unstoppable juggernaut. They field a staggering array of units, including tanks, armored cars, infantry (foot and mechanized), paratroopers, commandos, artillery (towed and self-propelled) and anti-tank guns, backed by fighters, bombers, battleships and destroyers. They enjoy far more firepower and mobility than the Japanese, whose army is mostly a First World War-style force of foot infantry and artillery.
But the unstoppable Allied war machine soon clanks to a halt. For starters, the terrain is not friendly to a mechanized army. In Japan ’45, the map of Kyushu is studded with rice paddies, forests, hills, villages, rivers and streams. The terrain restricts movement to a crawl, and provides natural defensive cover for the defenders. Despite all those Allied Sherman tanks, there will be no dashing Patton-esque blitzkriegs on Kyushu.
And what nature can’t provide, Japanese shovels will. The invasion beaches on Kyushu are studded with minefields, trenches, bunkers and pillboxes. The Allied player can only gnash his teeth as bombs, napalm and one-ton shells from battleships barely scratch Japanese troops embedded deep in their fortifications.
Finally, there is the Japanese soldier to contend with. The core of the Imperial Army was its legendarily tough infantry, which could withstand the hardest privations, and preferred to fight hand-to-hand with the bayonet. Even if their weapons aren’t quite as good or plentiful as Allied equipment, they’re good enough to inflict massive casualties on the invaders.
Playing Japan ’45, as the Allies against the AI-controlled Japanese side, graphically demonstrates that Operation Olympic would have been a meatgrinder. U.S. Army and Marine assault troops splashing ashore suffer heavy losses from minefields, artillery and machine guns. Pinned down on the exposed beaches, the riflemen and engineers advance inch-by-inch. Eventually the Japanese are dislodged from their entrenchments, and once in the open, they are vulnerable to Allied air and naval firepower.
But then what? The terrain on Kyushu is too rough and restricted to allow an Allied breakthrough. Once the Japanese defenders are pushed off the bushes, they just regroup inland among the hills and woods, and the Allies have to dig them out again.
The game suggests the invasion of Japan might have resembled the Okinawa campaign, where U.S. troops had to battle through multiple Japanese defensive lines in a grinding battle of attrition that cost 50,000 American casualties – and 400 ships sunk or damaged by kamikazes – before Okinawa was conquered. Like Okinawa, the question is not whether the Allies will capture Kyushu, but what price they will pay for it.
Which is really what an invasion of Japan would have boiled down to. That Japan was being invaded at all was proof that the war was lost. As an island nation, Japan’s first line of defense was the Imperial navy and air force, and both of these were rusting on the bottom of the Pacific or in remote jungles.
Short of surrender, the best the Japanese could hope was a divine miracle (and in fact, a massive typhoon in October 1945 would have badly disrupted Allied invasion plans). Or, to inflict so many casualties as to induce the Allies to a negotiated peace. But after so many years of bloodshed, the Allied nations were in no mood to negotiate anything else than Japanese surrender.
In the end, Japan gave up before invasion was necessary. A fact for which many Americans and Japanese had cause to be thankful.