The problem of disarmament has hitherto been approached chiefly from the political and economic side, and there is great danger that at the coming conference it will again be treated according to the needs of opposing international alignments. Thus far discussion on the basis of quantity and cost has not been very hopeful, and Major Lefebure's book should therefore be all the more welcome, for it takes up the problem from a very different angle, namely the technical, scientific. The author has had wide experience of chemical warfare and its development, and is quite right in stressing the uselessness of working out control of present armaments so long as nothing is done to regulate the employment of new inventions, more deadly than the old, which appear with alarming rapidity. The main argument of the book is that the effort must be made to control armaments which are readily made available. The other types can be used for national security, for agencies of war which require a long period for preparation reduce the immediate danger of conflict in as much as they involve a time period during which the machinery for preventing war may function. It must be confessed that in the details the exposition is not always as clear as it might be, but this book is undoubtedly an important contribution to the subject, and one which deserves wide attention.