JF Ptak Science Books (An earlier post from 2010, revised) [Atomic and Nuclear Weapons Series]
This post is one in a continuing series on the history of holes–the appearance of this particular hole meant the difference of life and death for hundreds of thousands of people, and it killed almost as many people as it didn’t kill.
The hole was in a cloud. It was a corollary cloud to missing clouds from a few days earlier.
On 6 August, 1945, the primary target of the first atomic bomb to be dropped on Japan was Hiroshima1–had there been unfavorable weather conditions, had the target been obscured by clouds or haze, a second target would be engaged–that was the Kokura Arsenal on the north shore of Kyushu. But conditions were bomb-favorable on that day, and Hiroshima was the city that was killed. Little Boy, the U-235 bomb dropped by Paul Tibbets from the Enola Gay exploded 1,900 feet above Hiroshima. The bomb detonated and–with blast and shock wave and the ensuing damage and conflagration–70,000-80.000 people were killed (and at least double that number within five years).
It was a day before the news of the bombing was verified for Tokyo, and another day before the Big Six leaders of the Japanese army and government decided that they couldn’t decide in what to do with the Potsdam declarations and order of surrender. It was a raging debate among those leaders, and it was a failure.
The second bomb, the plutonium Fat Man, was to be dropped by Major Charles Sweeney from Frederick Bock’s B-29 Superfortress Bockscar on the next target, which was decided to be the Kokura Arsenal. And so Fat Man was taken over Kokura on 9 August, but by the time Major Sweeney (who had piloted the Great Artiste behind the Enola Gay on the Hiroshima bombing) had arrived the previously comfortable atmospheric conditions had turned cloudy, overcast, the target obscured. Sweeney made three runs over the target, but it stayed hidden from the bombardier, and so the people of Kokura were spared. Major Sweeney tuned to his secondary target, Nagasaki. With fuel running out, the clouds were also running thick over Nagasaki, until the last moment, when a hole opened in the canopy and the bomb was released through it, exploding with the impact of 22,000 tons of TNT at about 1640 feet above the city, killing 70,000 people (by the end of the year, 140,000 by 1950).
The hills around Nagasaki confined the blast and protected those on the other side of them. Kokura had no such terrain, which means that had the bomb been dropped there, even more people would have been killed outright and many more so over time.
The hole theory though is not necessarily complete--there may not have been a hole. Nobelist (physics) Luis Alvarez, who made major contributions to the firing mechanism for the weapon and a genius-in-general, and who flew as part of an Aerial Observation Team to assess the yield of the bombs, thought that perhaps there was a hole in the clouds and perhaps there wasn't--"ostensibly" there was a hole, he wrote. Perhaps the bombardier saw the target, and perhaps not. In his Adventures of a Physicist (1989), Alvarez writes about the misery and the snaufedness of the mission, the clouds over Kokura and the multiple runs, the very low fuel which allowed only for one run on the Nagasaki secondary, and the growing accuracy of the flak from below. On page 145 he states that pilot Sweeny had decided against orders to attempt a radar-guided bombing of the 80% cloud-covered target--until suddenly the famous hole appeared, and bombardier Kermit Behan found the target and released the weapon. Alvarez records that the bomb detonated about 2 miles off-target, which he said would have been a "reasonable error" for a radar-controlled drop, which would fit nicely with the his claim that Behan was Air Forces's "best bombardier". Alvarez said that he took the report of the hole "with a grain of salt"2. (See extract below.)
In any event, some sort of hole opened for Nagasaki, and closed for Kokura.
It is interesting to note that "the luck of Kokura" or "Kokura luck" is a translated Japanese euphemism for the unknown avoidance of disaster, of escaping a tremendous fate without knowing it. (This appears often on the internet though I am using as a source The History and Science of the Manhattan Project, by Bruce Cameron Reed, Springer, 2014, pg 400.)
New York Times correspondent William L. Laurence flew in the Great Artiste, following Bockscar that delivered the bomb 1640 feet over Nagasaki. His report on Nagasaki appeared a month later in the newspaper, and the full text is available via the Atomic Archive blog here.
1. The targets discussed by the Targeting Committee (“Minutes of the second meeting of the Target Committee, Los Alamos, May 10-11, 1945") on 10 and 11 May 1945 included the following:
(1) Kyoto (the former capital with one million people, a center of religious and intellectual life in Japan This target is an urban industrial area with a population of 1,000,000. It is the former capital of Japan and many people and industries are now being moved there as other areas are being destroyed. From the psychological point of view there is the advantage that “Kyoto is an intellectual center for Japan and the people there are more apt to appreciate the significance of such a weapon as the gadget”; (2) Hiroshima (listed as an Army depot though “due to rivers it is not a good incendiary target”; (3) Yokohama (one of the largest remaining untouched industrial centers in Japan); (4) Kokura Arsenal (one of the largest in Japan and situated by urban industrial sprawl); (5) Nigata (port on Honshu) and (6)the Emperor’s palace (which was discussed as a possible target but dismissed almost immediately).[Yawata was also considered (as an industrial center) (during the preliminary meeting of the targeting committee on 2 May 1945) (along with Tokyo, Nagoya, Osaka, Kyoto, Kobe, Hiroshima and Nagasaki.]
The members of the targeting committee (source for this material is Gene Dannen at Dannen.com, transcribing targeting material of the U.S. National Archives, Record Group 77, Records of the Office of the Chief of Engineers, Manhattan Engineer District, TS Manhattan Project File '42-'46, folder 5D Selection of Targets, 2 Notes on Target Committee Meetings) included (on 10 May): "General Thomas Farrell, Dr. Charles C. Lauritsen, Colonel L.E. Seeman, Dr. Norman Ramsey, Captain Parsons, Dr. Robert L. Dennison, Major John A. Derry, Dr. John von Neumann, Dr. Stearns, Dr. Robert R. Wilson, Dr. Richard C. Tolman, Dr. William G. Penney, Dr. Robert Oppenheimer." In attendance for the 11 May discussion was Dr.Hans Bethe and Dr. Brode, plus: Colonel Seeman, Dr. Stearns, Captain William S. Parsons, Dr. John von Neumann, Major Derr, Dr. Robert L. Dennison, Dr. Richard C. Tolman, Dr. Penney, Dr. Oppenheimer , Dr. Ramsey and Dr. Wilson."
2. Alvarez on the hole: