If the jelled material is too soft or too weak, then it won’t actually deliver a very large amount of radiation to whatever it’s sticking to. You can think of a Molotov cocktail that’s filled up with gasoline, exploding and delivering gasoline. It can burn somebody or something quite terribly, but the fire will go out relatively quickly. Whereas by contrast, if napalm is thrown on something, it will stick to it.
A gel that was too loose would produce what they described dismissively as applesauce. In other words, it wasn’t thick enough or solid enough in its globules to adhere to something. And something that was just right would form quite large-size chunks. It had to be a balance between too thick and too thin and just right. And that’s what they ultimately hit upon with napalm.
Neer and I visited the Harvard soccer field, right behind the business school, which is across the river from the main campus. It’s where Hershberg and Fieser tested napalm in 1942. Hershberg had figured out how to turn their new gel into a bomb: by inserting a stick of TNT with a layer of white phosphorus wrapped around it in the middle of a canister of napalm. Phosphorus burns at a very high temperature, so the TNT would go off, driving the burning phosphorus into the napalm gel, igniting it, and sending globs of it in every direction. For a bomb case, they used a shell that had originally been designed to hold mustard gas. Robert Neer described the scene:
It was on Independence Day, 1942. They had finalized the formulation for the gel incendiary on Valentine’s Day, February 14. And then they figured out the white-phosphorus-burster ignition system and got the bomb shells from the military and built their prototypes.
They dug a lagoon into the field. The lagoon was, I believe, about a hundred feet in diameter. It was quite a substantial lagoon because they didn’t want anybody to get hurt. And they had this pretty large napalm bomb in a canister that they were going to explode in the center. So they put the bomb right in the center of this lagoon, which had been filled up with water by some trucks from the Cambridge Fire Department.
The birth of napalm. Baptized in eight inches of water in the middle of Harvard’s soccer pitch. When he was doing his research, Robert Neer spotted a little detail in the photos from that day.
In the initial pictures of the test, there are people dressed in whites playing on the tennis courts. And then after the bomb goes off, you see that the tennis courts are abandoned…So maybe they told everybody that they were about to test this napalm bomb, or maybe they just let them keep playing tennis and then tested it and everybody ran away. I don’t know. Nobody was injured in these tests. After the bomb was exploded, they made a very careful catalog of the distribution and size of the extinguished globules of napalm, because that was part of determining the most effective consistency of the gel.
Fieser and Hershberg took their creation back to the National Defense Research Committee, and Hottel realized he had finally found what they were all looking for: napalm, created at Harvard University, perfected in the fields along the meandering Charles River.
2.
There was never any question what napalm was for. It was intended to be used against Japan.
A few months after Pearl Harbor, two American analysts published an essay in Harper’s Magazine. When it comes time to retaliate against Japan, the authors argued, there’s a really easy way to do it. Fire. Osaka was their case study. Osaka’s streets are very narrow. Narrow streets means that fire can jump easily from one side to the other. And the city didn’t have a lot of parks that could act as firebreaks.
Plus, unlike Western cities, Japanese cities weren’t built of bricks and mortar. The beams, joists, and floorboards of houses were all wooden. Ceilings were made of heavy paper soaked in fish oil. Walls were made of wood or thin stucco. Inside were tatami—straw mats. Japanese houses were tinderboxes.
As the analysts wrote, “After some considerable calculation, we have determined that the combustible coverage in the twenty-five-square-mile area that is the central section of Osaka is 80 percent, as opposed to 15 percent for London.”
Eighty percent—that’s almost the whole city.
The people writing the article weren’t military officers or White House policy makers. The idea that you might destroy 80 percent of one of your enemy’s cities—burn it to the ground—was heretical. William Sherman, the general who led the Union Army on its final devastating course through the South after the Civil War, famously burned down Atlanta. But not all of Atlanta. The business and industrial districts. Not civilians in their homes. In the aftermath of Pearl Harbor, however, this heretical idea began to seem less heretical. Didn’t a lot of Japanese industrial production actually take place in people’s houses? Wasn’t it true that a lot of the war effort happened in living rooms as well as factories? A gradual process of rationalization began to take hold.