File:Groves memo 30oct43 p2.GIF

(2) As a gas warfare instrument the material would be ground into particles of microscopic size to form dust and smoke and distributed by a ground-fired projectile, land vehicles, or aerial bombs. In this form it would be inhaled by personnel. The amount necessary to cause death to a person inhaling the material is extremely small. It has been estimated that one millionth of a gram accumulating in a person's body would be fatal. There are no known methods of treatment for such a casualty

Two factors appear to increase the effectiveness of radioactive dust or smoke as a weapon. These are: (1) It cannot be detected by the senses; (2) It can be distributed in a dust or smoke form so finely powdered that it will permeate a standard gas mask filter in quantities large enough to be extremely damaging. An off-setting factor in its effectiveness as a weapon is that in a dust or smoke form the material is so finely pulverized that it takes on the characteristic of a quickly dissipating gas and is therefore subject to all the factors (such as wind) working against maintenance of high concentrations for more than a few minutes over a given area.

c. Possible Use by the Enemy.

It is felt that radioactive warfare can be used by the Germans for the following purposes:

(1) To make evacuated areas uninhabitable.

(2) To contaminate small critical areas such as rail-road yards and airports.

(3) As a radioactive poison gas to create casualties among troops.

(4) Against large cities, to promote panic, and create casualties among civilian populations.

For use in cities, it is estimated that concentrations would have to be extremely high to offset the shielding effect of buildings

Doctors Compton and Urey, two members of the Committee, felt that radioactive material may be used by the Germans against United Nations in the autumn of 1943. Dr. Conant apparently does not concur in this opinion.

d. Possible Use by the United States.

It is the recommendation of this Subcommittee that if military authorities feel that the United States should be ready to use radioactive weapons in case the enemy started it first, studies on the subject should be started immediately.