
A B-29 releases incendiary bombs on Yokohama in May 1945 (image via National Museum of US Air Force)
Hiroshima on the morning of August 6, 1945, was bright, sunny, and perhaps a little uncomfortably warm. Except for a lingering anxiety among its residents that they were due for something special — Hiroshima had been spared the air raids and firebombs launched that summer against its neighbors — there was but the passing buzz of American B-29s to suggest anything to be concerned about. Several days earlier, much of Japan, including Hiroshima, was showered by American forces with millions of leaflets, each containing a seemingly humanitarian plea to evacuate the citizens of twelve cities named on the leaflet’s reverse side. There are three known versions of this leaflet, designed by General Curtis LeMay, and the cities named were almost all of questionable military or economic value. Hiroshima was not among them. At 8:15 in the morning, the city was leveled by the “brief reincarnations of distant suns.”

Messages written on the back of a LeMay leaflet (click to enlarge) (image via Gifu Prefecture)
The “LeMay leaflet,” as it has become known, was twenty-one centimeters wide and fourteen centimeters high. It was printed in black-and-white, and features a fearsome photograph of five Boeing B-29 Superfortress bombers casually dropping their payloads onto unseen targets. The image was taken from an air raid over Yokohama — a cropped version, officially released by the Air Force, contains fewer bombers — which occurred on May 29th, 1945, and killed as many as 8,000 people. The incendiary bombs appear to be falling directly on a half-border of tidy circles, illustrations superimposed over the photograph that contain the names of eleven or twelve cities. The other side of the leaflet is dedicated to a long, stern appeal to the hypothetical civilian discovering it, and explains that “America is not fighting the Japanese people but is fighting the military clique which has enslaved the Japanese people,” urging civilians, in no certain terms, to evacuate.
In 1958, the Operations Research Office, a department of Johns Hopkins funded by the United States military, commissioned William E. Daugherty, one of its employees, to document the use and effectiveness of military propaganda. The resulting work, exhaustively compiled by Daugherty, was called A Psychological Warfare Casebook, and describes the LeMay leafleting as having occurred on three separate days. The following leaflet was dropped on July 27:

Image of LeMay leaflet, counter-clockwise, the circles read: Tokyo, Ujiyamada, Tsu, Koriyama, Hakodate, Nagaoka, Uwajima, Kurume, Ichinomiya, Ogaki, Nishinomiya, and Aomori (image via papersleuth.com)
The next day, half of these cities — Aomori, Ichinomiya, Tsu, Ujiyamada, Ōgaki, and Uwajima — were subjected to firebombing, and thousands were killed.
Daugherty writes that Japanese cities were next leafleted on July 30 and again on August 1. A report on the Central Intelligence Agency’s “Studies in Intelligence” website also claims that leaflets were dropped “on 33 cities,” including Hiroshima and Nagasaki, on August 3.

LeMay leaflet; counter-clockwise, the text reads: Nagano, Takaoka, Kurume, Fukuyama, Toyama, Maizuru, Otsu, Nishinomiya, Maebashi, Koriyama, Hachioji, and Mito (image via cia.gov)
These leaflets contain, with some exceptions, a different set of cities, but their design and the message on the back have not changed. On August 1, Mito, Hachioji, and Nagaoka were bombed, and Toyama, Maebashi, and Saga followed in the days after. The next Monday saw the first use of the atomic bomb in human history, and that following Thursday the second. The Imperial Army of Japan continued to fight until August 15, and the firebombings continued until then, most against cities warned on the leaflets, but also against some which were not. In several cases, such as with Akita, cities were not targeted for an air raid until more than two weeks after being named on a leaflet.
Daugherty makes clear that the leaflets were successful in one aspect: they managed to scare the citizens, not save them. As people attempted to evacuate, wartime production halted, and the movement of noncombatants tied up the military forces, leading to the “further breakdown of social structure in Japanese communities.” When the B-29s finally arrived, whether carrying incendiary devices, nuclear bombs, or simply more leaflets, there was little either the army or the civilians could do. As Daugherty, whose book was explicitly written to “meet the particular needs of Army personnel,” explains, “Warnings … tend to increase the impact of lethal weapons.” In the ensuing chaos and confusion, the US military could hope for even more casualties. But in the case of Hiroshima and Nagasaki, which were never named on the leaflets they received, the humanitarian pretense was dropped entirely. Small wonder that nobody expected what was to come.

Leaflets disguised as money so as to attract civilians (image via cia.gov)

Soldiers packaging up leaflets for distribution (image via cia.gov)