My dear P.M.,

Whilst in Vienna I heard several versions, varying only in detail,
of the civil disturbance that occurred there this year, in which
nearly one hundred people were killed mostly by rifle and machine
gun fire turned on them by the police. [1] The story is of no
great moment, other than that of being a particularly good example
of how police can infuriate a stupid and rather aimless mob who
want to 'demonstrate' and probably make a bit of trouble. One
thing led to another in this case in perfect sequence until
shooting started, and then became blind and indiscriminate. I have
always thought that tear-gas bombs would be ideal for coping with
this type of disturbance, and I see no reason why police
authorities do not make provision for the simple training of their
personnel in their use -keeping the actual bombs in store for
issue in emergency, just as lethal weapons are now kept ready for
issue. Rifle and machine gun fire on a mob seems to be an inhuman
and unnecessary proceeding when other more suitable methods are
available.

In this respect I have looked up C.I.D. Paper 760-B of January
1927, the essential part of which I reproduce below:-

It is for consideration whether the armed forces of the Crown in
China should be supplied with tear gas for use against mobs, as
being more humane, as effective and less likely to cause
diplomatic difficulties than lethal weapons.

In the Washington Agreement and recent Geneva Protocol on the
subject of gas, it is laid down that gas is not to be used in war;

tear gas is included in this prohibition.

That this prohibition does not apply in peace time is apparently
the view of certain nations, as authentic information of its use
by France and the United States in quelling civil disturbances has
been received.

This attitude is only logical, for it is far more humane and,
under most circumstances, just as effective as the use of lethal
weapons.

The tear gas used by us during the war is a liquid known as S.K.,
the vapour from which produces the effect. It is not suitable for
use against mobs as, being a liquid, its effect may persist in the
locality where it is applied for hours and even days, also a
splash of the liquid in the eye may cause permanent blindness. A
more suitable tear gas is one known as C.A.P., which is non-
persistent and cannot cause any permanent injury. Unfortunately
the only stocks of tear gas in this country are of S.K., and no
facilities exist for the immediate production of C.A.P.

This latter gas, and suitable means for using it in the form of
small cartridges in police batons and small hand grenades, could,
if desired, be purchased on the open market in America.

Possible retaliation by the Cantonese [2] with more lethal gases
than tear gas must be considered. With regard to this,
intelligence reports indicate that they have a laboratory engaged
in poison gas research in the Whampoa Military School [3], but
that their stocks of gas are small. They also are known to have
been supplied with a few hundred Russian gas masks. On the other
hand, if they are permitted to receive unrestricted supplies of
munitions from Russia, that country could supply them with gas in
quantity.

Our gas mask, which has been supplied to all the naval personnel,
is proof against all gases that could be used by the Chinese.

Should supply of tear gas be agreed to, it is suggested that very
definite instructions as to the circumstances under which it
should be used should be given.

Yours sincerely,
R. G. CASEY