Napalm Bombs Over Japan - The M-69

Napalm Bombs Over Japan - The M-69

B-29s, flying over Japan, dropped napalm-filled cluster bombs known as the M-69.  Stewart Halsey Ross—in his book, Strategic Bombing by the United States in World War II: The Myths and the Facts—describes this devastating weapon, as follows:

...the M-69, [was] a 6.2 pound napalm bomblet of sophisticated design.  Napalm was the remarkable material that had been developed by DuPont expressly as a filler for incendiary bombs, as a substitute for commonly used magnesium, the lightweight metal increasingly used in aircraft components. 

The name was derived from its chemical compound, a mixture of naphthene and palmitic acids.  This new compound when mixed with gasoline produced a thick, sticky, jelly-like material. 

Napalm would revolutionize air-dropped incendiary weapons and would be used with equally devastating effect in flamethrowers by U.S. Marines in the Pacific war against Japanese troops. 

By 1945, an enhanced formula, Napalm B, had been introduced; chemists added polystyrene and benzene to the lethal brew, yielding a longer burning fire at temperatures up to 2,000 degrees Fahrenheit, and even greater stickiness.
In external appearance the M-69 was deceptively innocent looking, disguising its sophisticated destructive capabilities inside a 3-inch-diameter, 20-inch-long plain steel cylinder.  There were no stabilizing tail fins to make it look like a bomb; instead it contained a 3-foot-long strip of cloth, like a kite's tail, that popped out when it deployed to prevent tumbling.

As the sturdy unit punched its way through the thin roof of a house, a time-delay fuse was activated which, after 3 to 5 seconds, detonated an ejection-ignition charge.  By this time, the bomblet would be at rest, on its side or its nose embedded in a floor.  

The exploding charge ignited a small quantity of white-phosphorous powder which instantly set fire to the napalm and at the same time blew a fiercely burning glob of gasoline gel out of the tail of the casing.  The burning gel could be propelled as far out as 100 feet.  Whatever the glob hit, it stuck to; if the material was combustible, it immediately started an intense, hard-to-extinguish fire.

M-69 bombs were bound together in clusters of 38 and fitted inside a finned thin-walled container that opened clamshell-like over the target, scattering the bomblets.  A primacord charge ran through the container's flange that was time-fuzed to explode and open the cluster at a predetermined altitude, generally about 2000 feet, an altitude that tests had shown yielded optimum dispersion.

A simpler, lighter construction was merely to strap the bombs together and attach a tail fin.  The primacord cut the straps at fuze ignition, allowing the individual bombs to freely disperse.

Such configurations were not as aerodynamically stable as the "containerized" bomblets, but incendiary bombs were large-area weapons and were notoriously inaccurate.

Depending on aircraft speed and winds close to the ground, the bombs would be spread out over a keyhold-shaped area about 500 feet wide at its widest by about a half-mile long.  A single B-29 on a firebomb raid over Japan typically would carry 40 clusters, or about 1,500 individual M-69s.

Dropping fire bombs over Japan intensified during March of 1945. Beginning on the 9th of that month, the M-69 caused massive damage in Tokyo. Around 9,700 acres (or roughly 15 square miles) fell victim to the American attack.


General Curtis Lemay issued a statement, accompanied by pictures, regarding the March 9-10 bombing of Tokyo:

The B-29s from bases on Saipan, Tinian and Guam attacked with incendiary bombs in the early hours of Saturday, March 10, an urban industrial area of Tokyo consisting of ten square miles, centered about 10,000 feet east northeast of the Emperor’s Palace. The Palace itself was not a target.


The area attacked is now entirely burned out and an area of five square miles surrounding it is similarly gutted by fire. This fire left nothing but twisted, tumbled-down rubble in its path. These facts are incontrovertibly established by reconnaissance photographs taken on the afternoon of the strike.

The area totally destroyed by this incendiary strike, clearly identifiable in these photographs, covers a total of 422,500 square feet, which is approximately 9,700 acres, or fifteen square miles.

Other identifiable industrial and urban targets lie in ruins within the destroyed area, including the previously damaged Ueno rail road station, the Rising Sun Petroleum Terminal, the Ogura Oil Company, the Nisshin Spinning Mill, the Japan Machine Industry, the Marunouchi telephone exchange, Kanda Market and Hattori Company.

Hundreds of small business establishments directly concerned with the war industry, many important administrative buildings and other thousands of home industries were also in the area wiped out.


What, according to Lemay, could have explained this incendiary attack over Tokyo? The General believed that it would shorten the war:

So much for the facts of accomplishments, the statistics of devastation. As the commander of the air crew members who flew and fought this mission and as the commander of the other officers and men who by their work on the ground at our bases here in the Marianas made this mission possible, I have something else to say at this time. What I want to say is not easy to say. I shall try to say it as if I were saying it to the people at home who belong to my officers and men and to whom my officers and men belong.

I believe that all those under my command on these island bases have by their participation in this single operation shortened this war. To what extent they have shortened it no one can tell, but I believe that if there has been cut from its duration only one day or one hour my officers and men have served a high purpose.

They will pursue that purpose stubbornly. They are fighting for a quicker end to this war, and all will continue to fight for a quicker end to it with all the brains and strength they have. (Lemay, quoted in a New York Times article, by Warren Moscow, entitled “Center of Tokyo Devastated by Fire Bombs,” published on March 11, 1945. The article is included in The New York Times Living History: World War II: The Allied Counteroffensive, 1942-1945, edited by Douglas Brinkley, at pages 280-282.)

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Author: Carole D. Bos, J.D. 5183stories and lessons created

Original Release: Oct 07, 2013

Updated Last Revision: Nov 13, 2019

Media Credits

Quoted passage from Strategic Bombing by the United States in World War II: The Myths and the Facts, by Stewart Halsey Ross, page 108. In-text photos from Wikimedia Commons (including in a Wikipedia article on "Bombing of Tokyo").


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"Napalm Bombs Over Japan - The M-69" AwesomeStories.com. Oct 07, 2013. Nov 13, 2019.
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