Operation Downfall was the codename for the planned Allied invasion of Japan in 1945, which never occurred due to Japan’s surrender after the atomic bombings of Hiroshima and Nagasaki. However, had the operation gone ahead, it would have been one of the most massive military campaigns in history. The Allies had prepared a wide range of new and experimental weapons, some of which were intended to give them a decisive advantage in the invasion of the Japanese home islands.
Here’s a look at some of the notable new war machine weapons the Allies were planning to use in Operation Downfall:
1. The Atomic Bomb
By 1945, the U.S. had developed the atomic bomb under the secret Manhattan Project. Though the bombs were dropped on Hiroshima and Nagasaki in August 1945, they were originally part of the arsenal planned for use in Operation Downfall if Japan had not surrendered. The atomic bombs were intended to be used on key Japanese cities, particularly Tokyo, to break Japan's will to continue fighting. The bombs represented the ultimate weapon in the Allied arsenal and could have dramatically shortened the war by forcing a swift Japanese surrender.
2. The B-29 Superfortress
The B-29 Superfortress was a long-range heavy bomber that had already been used in the Pacific theater for strategic bombing campaigns, including the atomic bombings. For Operation Downfall, the B-29 was to play a key role in the sustained bombing of Japan, targeting military installations, factories, and cities in an effort to destroy Japan’s war-making capacity. The B-29’s range, payload capacity, and ability to carry the atomic bomb made it an essential part of the Allied strategy.
3. The Landing Ship Tank (LST)
LSTs were large, flat-bottomed ships designed to land troops and supplies directly onto beaches, bypassing traditional port facilities. These vessels would have been central to the amphibious assault on the Japanese home islands, particularly in the first phase of the invasion of Kyushu (Operation Olympic) and later Honshu (Operation Coronet). While LSTs were already in use in World War II, their capacity for carrying massive amounts of troops and equipment would have been crucial for sustaining the large-scale invasions planned for Operation Downfall.
4. The Landing Craft, Vehicle, and Personnel (LCVP) - "Higgins Boat"
The LCVP, also known as the Higgins Boat, was an amphibious assault craft that had been widely used in the D-Day landings in Europe. For Operation Downfall, the LCVPs would have been used to ferry soldiers and equipment from ship to shore during the invasion of Japan. These boats were essential for the success of large amphibious operations due to their ability to land directly on beaches without needing a dock.
5. The M26 Pershing Tank
The M26 Pershing was a heavy tank developed late in World War II. Its powerful 90mm gun and thick armor made it capable of taking on Japan's armored forces and fortifications. While not yet in widespread deployment during the European campaign, the Pershing was slated to be used in Operation Downfall for ground assaults and the destruction of Japanese defensive positions. Its firepower and survivability made it a key asset for any land-based invasion.
6. Napalm and Incendiary Bombs
The U.S. had already used napalm in the Pacific War, notably in the bombing of Japan’s cities, such as the firebombing of Tokyo. For Operation Downfall, the use of napalm and incendiary bombs was planned to destroy Japanese cities and military installations, causing widespread destruction and civilian casualties. This was intended to weaken Japan’s resolve and infrastructure, similar to the Allied bombing campaigns in Europe.
7. The T29 Super Heavy Tank
The T29 was an experimental super-heavy tank designed for use against heavily fortified positions. Weighing in at 95 tons, the T29 was armed with a massive 105mm gun and was designed to overcome Japan’s formidable coastal defenses. However, the tank was never used in combat and was still in testing phases. Had Operation Downfall been launched, the T29 would have been employed in specialized assaults against Japan’s heavily fortified defenses, although it had limited practical deployment potential due to its size and logistical challenges.
8. The V-2 Rocket (Captured Technology)