On March 10, 1945, US Army Air Forces B-29 Superfortress bombers attacked Tokyo, dropping 1,700 tons of incendiary bombs on a city built largely of wood. The resulting conflagration killed as many as 100,000 people and left 1 million homeless. While the atomic attacks on Hiroshima and Nagasaki receive more attention, this attack, along with later firebombing raids on other Japanese cities, were far more destructive.
B-29 Superfortress bombers drop incendiary bombs on Japan, 1945
Late in WWII, as the island hopping campaign brought the Allies closer and closer to the island of Japan, bombing raids were increased against Japan's manufacturing assets. Unlike the US and European countries, where manufacturing was centered in large factories, Japan's war materiel was largely produced in homes and small factories as a cottage industry. Precision bombing from high altitudes was largely ineffective. So General Curtis LeMay, a veteran of Eighth Air Force bombing attacks against Germany and now in charge of all strategic air operations against the Japanese home islands, turned to low-level firebombing.
M-69 incendiary bombs loaded in a B-29 Superfortress
Precision bombing was normally carried out from high altitude and during the day. For the Tokyo raids, the bombers flew at altitudes of 5000-8000 feet, and at night. Accuracy was not required. In order to increase the carrying capacity of the bombers, all defensive armament was removed. By 1945, Japanese aerial defenses against attack were sparse, and night attacks made antiaircraft artillery less effective. The Superfortresses were armed with M-69 incendiary bombs. A single M-69 munition weighed only 6 pounds, but was dropped inside canisters that held 38 each. After dropping, the container would automatically open, spreading the smaller bombs, which were ignited on contact with the ground. Normally, each B-29 carried 37 canisters, totaling 1,400 individual munitions per plane. When the bombs ignited, they spread a jellied gasoline compound that was highly flammable.
Tokyo was chosen as the target for the first raid, codenamed Operation Meetinghouse. On March 9, 1945, 346 B-29s left Guam to attack Tokyo. Arriving at 2:00 am on March 10 (Guam time) over the city, 279 bombers dropped almost 1700 tons of bombs. The resulting firestorm destroyed 16 square miles of buildings, or 7% of the city's urban area. The fires burned so fiercely that many of those killed were suffocated, as the fires consumed so much oxygen. At the time, Tokyo police estimated that 83,793 people were killed, another 41,000 injured and another 1 million left homeless. Postwar estimates are as high as 100,000 killed. The USAAF lost 14 aircraft, less than the 5% loss rate that was considered acceptable.
Aerial photo of Tokyo following the war
The firebombing raids continued, in the belief that the attacks would lead the Japanese government to capitulate. They did not. According to one estimate, the firebombing campaign resulted in the destruction of 180 square miles in 67 cities, and killed more than 300,000 people. At the time, there were few moral qualms about destroying such large areas of the cities, along with their civilian populations. Military planners believed that these raids would shorten the war and save American lives by preventing a costly invasion of the Japanese home island. It wasn't until the nuclear attacks on Hiroshima and Nagasaki that the war finally ended, even though there were two more firebombing raids after Nagasaki.