NSSA BOMB DOC 73:
General Hull and Colonel Seaman - 1325 - 13 Aug 45
H What General Marshall wants to know is the status of the development of these bombs now so we can best determine how to use them. There's one of them due up the 23d as I recall it.
S There’s one ready to be shipped - waiting on order right now.
H The Question arises as to whether to start in the movement of them out there according to the old schedule or whether they should be shipping in accordance with our next operation. Two of them have had a tremendous effect on the Japan-ese as far as capitulation is concerned. The next one won’t be effective in that respect. In other words, the Japs will or will not. General Marshall feels we should consider now whether or not dropping them as originally planned, or these we have now should be held back for use in direct support of major operations but their dropping should be in conformity with their priority. That's the idea. What we want to know is what the program is now so we can report on it.
S The whole program is phased according to the best production. There is one of them that is ready to be shipped right now. The order was given Thursday and it should be ready the 19th.
H If the order is given now, when can it be ready?
S Thursday would be its readiness; the 19th it would be dropped.
H In other words, three or four days advance notice before it can be shipped, and six days after that when it can be dropped.
S That's figuring it so it will be safe. Then there will be another one the first part of September. Then there are three definite. There is a possibility of a fourth one in September, either the middle or the latter part.
H Now, how many in October?
S Probably three in October.
H That’s three definite, possibly four by the end of September; possibly three more by the end of October; making a total possibility of seven. That is the information I want.
S So you can figure on three a month with a possibility of a fourth one. If you get the fourth one, you won’t get it next month. That is up to November.
H The last one, which is a possibility for the end of October, could you count in that for use before the end of October?
S You have a possibility of seven, with a good chance of using them prior to the 31st of October.
H They come out approximately at the rate of three a month.
S We are still in the midst of development - you will appreciate that. The possibility will have to be considered that there might be a dud. Going through the development, we are changing amounts and proportions of the active material so that certain ones may or will have lesser power. They may be more nearly equivalent to the one at Hiroshima than the one at Nagasaki.
H Tell me this - are they all coming out of the same pipeline or do you have two establishments?
S No, sir. It is out of the same pipeline.
H In other words, they will be spaced fairly evenly then; about one every ten days.
S The biggest gap will be between the one now and the one for the first part of September. After that, I would say approximately one every ten days.
H That will continue even after the first of November, we will say.
S Every ten days.
H That gives me the Information I want.
S Except in September, we can only count on three in September, counting the one n now. Don't figure the rate of three a month, until starting with October. One now, one definitely the first part of September, one the middle of September and possibly the latter part of September. Three from now until the end of September, and three a month thereafter.
H That gives me the information I want. Now, on each one of them, whatever the plan may be of decision, we can figure how long from the time it is produced until the time it is out there ready for use.
S From the time of its readiness here, I think we have been using six days. We have allowed for weather en route, possible change in air crew.
H That is the information I wanted. The problem now is whether or not, assuming the Japanese do not capitulate, continue on dropping them every time one is made and shipped out there or whether to hold them up as far as the dropping is con¬cerned and then pour them all on in a reasonably short time. Not all in one day, but over a short period. And that also takes into consideration the target that we are after. In other words should we not concentrate on targets that will be of the greatest assistance to an invasion rather than industry, morale, psychology, etc.
S Nearer the tactical use rather than other use.
H That is what it amounts to. What is your own personal reaction to that?
S I have studied that [r oom] deal. Our own troops would have to be about six miles away. I am not sure that the Air Forces could place it within 500 feet of the point we want. Of course, it is not that "pinpoint*. Then the stage of develop¬ment has to be considered. The work it is liable to be used for the more or less has to be the explosive effect. It would be just a gamble on putting or sending those troops through.
H Not the same day or anything like that. We might do it a couple or three days before. You plan to lead on a certain beach. Behind which you know there is a good road communication. and maybe a division or two of Japanese troops. Neutral¬ization of that at some time from H Hour of the landing back earlier, maybe a day or two or three. I don't anticipate you would be dropping it as we do other type bombs that are in support of the infantry. I am thinking about neutralizing a division or a communication center or some thing so that it would facilitate the movement ashore of troops.
S That is the preferable use at this time from that standpoint. The weapon we have is not a penetration weapon. The marksmanship is not as good as possible. It is much better than average workmanship. We are still developing it though.
H From this on more or loss of the timing factor, how much time before the troops actually as into that area do you think would be the safety factor? Suppose you did get a dud or an incomplete explosion, what safety factor should you consider, one, two, three days?
S I think we are sending some people over to actually measure that factor. I think certainly by within 48 hours that could be done. Everything is going so fast. We would like to train people and get them in a combat spirit to do that. I think the people we have are the best qualified in that line. Of course, as you say, if it is used back in a kind of reserve line or in a reserve position or a concentration area but that you wouldn't be up against right sway.
H I don't think you would land at eight o'clock in the morning and you would drop it at six o'clock, but the day before, even from the tactical standpoint without regard to when it fails to go off or something like that.
S Another thing you may be likely to consider is that while you are landing you might not want to use it as it could be a dud. It is not something that you fool around with.
H I would appreciate if you would discuss that angle with General Groves. I would like to have his slant on it. That is the question, how do we employ it and when do we employ it next? It has certainly served its purpose, those two we have used. I don’t think it could have been more useful than it has. If we had another one, today would be a good day to drop it. We don't have it ready. Anyhow within the next ten days the Japanese will make up their minds one way or the other so the psychological effect is lost so far as the next one is concerned in my opinion, pertaining to capitulation. Should we not lay off a while, and then group them one, two, three? I should like to get his slant on the thing, General Groves' slant.