War does not affect weather. Weather does affect war. To know in advance the climate of a war zone; to have as accurate knowledge as possible of the probability of occurrence of severe cold; of sudden thaws; of heavy rains; of great heat; of high winds--all this is a very essential element in planning a campaign or in organizing a single engagement. Picked troops, discipline, a well-organized system of transport, proper clothing--in short, all that goes to make up the most efficient military organization, is of supreme importance. But we must recognize the fact that the weather is by no means the least important of the many external factors which control military campaigns.

The present war has provided an unusual opportunity to study the influence of weather upon modern military operations. Each war zone has its own special climatic types, and present its own peculiar problems. On the western front, the chief difficulty has been the autumn and winter rains, not so much because these are unusually heavy, but because of their frequency. On the eastern front the winters are more severe than in the west. There has been more suffering on account of the cold, and because of snow storms. The importance of long spells of freezing weather, during which alone the marshes can be crossed, has been clearly seen. On the Austro-Italian front fighting has gone on in the midst of deep snows, avalanches, extreme cold, and violent storms. The Gallipoli campaign was carried on in the dry season and there was terrible suffering on account of lack of water.

The use of airplanes and of Zeppelins and of asphyxiating gas has given extraordinary emphasis to the importance of the weather factor in war. It is clear that the Germans had, from the start, a very efficient military field weather service, whose headquarters, for the western front, are in Belgium. Their meteorological observers have been making forecasts of the most favorable conditions for Zeppelin raids and for gas attacks.

We have many lessons to learn from the present war. One of these is the necessity of having trained meteorologists attached to our armies, and of giving our officers some instruction in the principles of meteorology and of weather forecasting.