The authors have not taken advantage of the opportunity to paint their story in lurid colors, with anecdotes and personal experience from the present war. Instead, they have presented the case of chemistry, as a factor in warfare, with restraint, caution and sufficient emphasis to drive home their points. The practical aspects of the place chemistry holds in the present emergency, against an historical background of the hows, whens and wheres chemistry has contributed to modern war. Chemistry is industrial America's first line of defence, and it enters every phase of war, -- feeding, clothing, shelter, protection, transportation and weapons, not to speak of the obvious value in medicine and disinfectants. The machines of warfare, the man-made man killers, the crucibles of death -- all step-children of chemistry as a constructive force. Finally, a cautious survey of the probabilities of chemistry in the present war, and an appraisal of the extent to which we are prepared to produce almost everything we need for modern chemical warfare with only two raw materials in insufficient quantity. The authors combine practical experience both in chemistry and the army.