One of the most astonishing paradoxes connected with the misapplication of human brains and energy glorified with the name of the “art of war” is this—that, while weather has always played an important part, and often a decisive one, in military operations, no attempt was ever made until a few years ago to include meteorology in the purview of military science or to utilize the services of meteorologists at the battle front.

The most casual survey of the history of warfare reveals the fact that atmospheric conditions rank high among the “controls” of fighting. From a military point of view, weather and climate bear a certain analogy to topography. They are a part of the physical environment with which a commander has to reckon. Weather, however, differs from topography in the fact that it is subject to rapid changes, and is therefore doubly worthy of attention on the part of an army, which must not only take account of the weather as observed and in progress, but must also, as far as possible, anticipate that which is to follow.

Everybody will recall the ruin that overtook the French army in Russia in 1812 on account of untoward weather conditions, but it is less well known that Napoleon, with his usual sagacity, obtained from his scientific advisers a report on the Russian climate before he planned his campaign; that the winter set in much earlier than usual in that fatal year; and, most interesting of all, that it was actually a brief period of thawing weather, rather than the intense cold that preceded and followed it, which, by turning the roads into bogs and breaking up the ice in the Beresina, brought about the culminating disaster.

Another fateful spell of weather ushered in the battle of Waterloo. It is described in a well-known passage of “Les MisÉrables,” which contains enough truth mingled with hyperbole to be worth quoting:

“S’il n’avait pas plu dans la nuit du 17 au 18 janvier, 1815, l’avenir de l’Europe Était changÉ. Quelques gouttes de plus ou de moins out fait pencher NapolÉon. Pour que Waterloo fÛt la fin d’Austerlitz, la Providence n’a eu besoin que d’un peu de pluie, et un nuage traversant le ciel À contre-sens de la saison a suffi pour l’Écroulement d’un monde.”

The rains and floods that led to the annihilation of the Roman legions under Varus in A.D. 9 and the great tempests that helped English seamen defeat the Spanish Armada furnish additional well-known examples of the immense importance of weather as a factor in warfare. We need not, however, look farther back than to the recent world conflict to find similar examples in profusion. Leaving out of consideration the indirect effects of the weather upon the progress of the war as exercised through its control of crops, transportation, and other features in the economic life of the belligerent and neutral nations, we need only examine war-time newspapers to see how the armies themselves were helped or harassed by meteorological conditions at every turn. The war was a great popular teacher of climatography, just as it was of geography. The drenching misery of Flemish winters, as formidable to the soldiers in the trenches as the bullets of the enemy, became as familiar to the present generation of Americans as did somewhat similar conditions in Virginia to Americans of the Civil War period.

The British campaigns in Mesopotamia were as much a conflict with climate as with human foes. Marches were made when the temperature stood at 110 degrees Fahrenheit and over. The temperature in the hospital tents is said to have reached 130 degrees. The disaster at Kut-el-Amara was due to the rains and floods that prevented reenforcements from reaching the beleaguered garrison. The failure of the Dardanelles expedition was partly due to the fact that the extreme dryness of the country was not realized—as it would have been if the War Office had called climatologists into council—and totally inadequate provision was made for the water supply.

The new engines of war brought forth by the recent struggle were peculiarly susceptible to the effects of weather. The larger guns and heavy motor trucks were difficult to move over muddy roads. The aircraft, though they managed to fly in all kinds of weather, suffered innumerable disasters for which atmospheric conditions—chiefly storms and fog—were responsible, and their operations were conspicuously affected by favorable and unfavorable winds. Shells were fired to unprecedented heights, and their trajectories were modified by unknown conditions in the upper air. Last but not least, the use of poisonous gases, especially in the period before gas clouds were largely replaced by gas shells, was dependent upon the occurrence of appropriate winds; and a slight miscalculation in this respect sometimes brought disaster to the troops using the gas.

It is not surprising that professional meteorologists played a part in the World War, but it is difficult to understand why meteorological units were not attached to all armies, at least when on active service, several decades before the year 1914. Meteorologists did, indeed, take a hand in one earlier conflict, but not as enrolled soldiers. During the Spanish-American War a special service was organized by the United States Weather Bureau to protect the American fleet in southern waters from unpleasant surprises in the shape of West India hurricanes. In the summer of 1898 a chain of observation stations was established by the Bureau around the Caribbean Sea. The service then inaugurated in consequence of the exigencies of war proved so valuable to shipping in time of peace that it has continued to operate, with some intermissions, down to the present day.

When the World War broke out, the only country that immediately put meteorologists, as such, into the field was Germany. The Germans were fortunate in having a far greater number of trained meteorologists at their disposal than had their enemies. There were chairs of meteorology in several German universities and high schools, and the numerous meteorological observatories and institutes of the Empire had provided occupation for a large amount of professional talent in this line. One of the first acts of the army that invaded Belgium was to establish an aerological service in that country.

The Entente countries were slow in adding meteorological units to their armies, but their civilian meteorological services were utilized to the utmost for military purposes from the beginning of the war. They at first worked under difficulties arising from the cessation of the customary weather reports from central Europe, but, to offset this disadvantage, the weather map was expanded in other directions, the number of daily hours of observation was increased, and eventually the forecasters in London and Paris acquired much better facilities for making their predictions than they had enjoyed in time of peace. The supply of weather information to the public was suspended, and great precautions were taken to prevent the reports of the Allied services from being utilized by the enemy. The German meteorologists were seriously hampered by the lack of reports from the westward. It has been asserted that such reports were sometimes obtained by radio from submarines stationed off the coast of Ireland, but such a service, if it existed, must have been fragmentary and unsatisfactory. That the Germans made many mistakes in their attempts to infer the atmospheric conditions over the British Isles from the limited weather map at their disposal is proved by the fact that their airships frequently crossed the Channel when, with an ampler knowledge of impending weather, they would certainly have remained at home. Several Zeppelins came to grief in the course of these ill-timed raids. One of the interesting routine duties of the British Meteorological Office during the war was to draw the weather map for a given moment as the Germans would probably draw it, with their curtailed set of telegraphic reports, and then predict the German prediction!

In the spring of 1915 a small meteorological section was organised in the British Army, and attached to the Royal Engineers. This force was afterward enlarged, and provided units for service on several battle fronts. The British also developed a naval meteorological service, which had existed in embryo before the war, and, eventually, a special meteorological service for the Royal Air Force. Analogous services were organized by the French and the Italians.

The United States Army and the United States Navy both established meteorological services not long after this country entered the war. The former was attached to the Signal Corps, and was partly officered and recruited from the Weather Bureau. A training school for army meteorologists was opened at College Station, Texas. Upward of 300 men were given instruction in this school, and most of them were sent overseas. The naval meteorological service was headed by the director of Blue Hill Observatory, and the junior officers received special training at that institution.

The varied activities carried on by these war-time units were so different from the traditional duties of meteorologists that they may be said to mark the advent of a new branch of applied science—Military Meteorology. They were, moreover, as we shall see, extremely fruitful of effects upon the science of meteorology in general.

In the principal battle zones the military weather men maintained a dense network of observation stations, the reports from which, combined with those received from the regular peace-time weather stations of the Allied and neutral countries, enabled the forecasters at headquarters to keep closely in touch with atmospheric changes. Observations of both surface and upper-air conditions were made at frequent intervals, and radiotelegraphy was largely used to insure prompt transmission of the reports. In general, weather maps were drawn four times a day. Information was distributed locally to the fighting units by telephone and otherwise.

The vast fleet of aircraft called into being by the war would, of itself, have imposed upon the military meteorologists the necessity of paying a great amount of attention to the upper air. Pilot balloons were sent up so frequently and at so many points that the aviators generally knew just what winds they would encounter aloft. Special arrangements were made to follow the progress across the country of the thundersqualls which constituted a serious danger to the “sausages,” or observation balloons, as well as to aeroplanes on the ground, and to hangars.

There was, however, another urgent reason for keeping a close watch of the winds and other atmospheric conditions at various levels above the earth’s surface. Experience acquired early in the war proved that old-fashioned methods of correcting the aim of artillery for meteorological disturbances were extremely inadequate for modern guns, the projectiles of which rise to altitudes of from 10,000 to 20,000 feet and encounter conditions quite different from those prevailing at the surface. The flight of a projectile is affected by the force and direction of the wind, and the density of the air through which it passes. Some modern projectiles remain in the air as long as 70 seconds, and a moderate wind blowing across the path of such a projectile may easily cause it to fall half a mile away from the point at which it would strike if fired in still air. One of the routine duties of the army weather service was to observe the winds and compute the air-densities at different heights wherever such information was required by the artillery. In order to facilitate the application of such data by the gunners ingenious methods were developed for computing what is known as the “ballistic wind.” This is a fictitious wind which, if affecting the projectile throughout its flight, would produce the same total deflective effect and effect on range as the various winds that the projectile actually encounters.

Meteorological observations were also of great importance in connection with the new process of locating distant guns known as “sound-ranging.” This process consists, briefly, in determining the exact instant of arrival at several points of the sound waves propagated through the air from the gun that is being located. If sound traveled at a uniform speed, these observations would show the exact distance of each of the observing points from the gun, and a simple geometrical construction would indicate the position of the latter. The speed of sound waves in the air is, however, affected by both wind and temperature. Accordingly, allowance had to be made for these varying factors, and the necessary data were supplied by the meteorological units.

The observation and prediction of winds favoring the use of poisonous gases by friend or foe was one of the most delicate tasks allotted to the army meteorologists. The flow of such gases is determined by the winds close to the surface of the earth, and these are greatly affected by topography. Local air currents controlled by the slope of the ground were especially utilized for gas attacks. Strong winds were unfavorable, because they quickly dissipated the gas cloud. The meteorologists not only advised their own troops when to use gas, but also gave warning when the atmospheric conditions were such that gas was likely to be used by the enemy. The use of gas shells was less dependent for its success upon the wind than the liberation of gas clouds, but even when shells were used the wind and weather at the objective point were factors of importance.

The exigencies of warfare developed several new features of meteorological practice, the utility of which did not cease with the war. Thus it became customary to measure the degree of “visibility” of distant objects, for the benefit of aviators and gunners, and this element was included in the routine weather reports. Scales of visibility, ranging from “very bad” to “excellent,” etc., were adopted, and eventually certain forms of apparatus (“visibility meters”) were devised for getting fairly precise measurements of this weather factor.

Another novel practice that deserves to be perpetuated was the plan adopted by the military forecasters of adding to their predictions a statement as to their probable accuracy; this was expressed on a numerical scale of “odds,” instead of by use of the vague terms “probably” and “possibly,” which have generally served the purpose of the dubious forecaster.

The war brought about many improvements in the instruments and methods used in sounding the upper air; and the intensive campaign of pilot-balloon observations carried out at the military stations provided a body of data for study quite unparalleled in the history of meteorology.

Lastly, the war revolutionized weather telegraphy in Europe. Before the war the European forecasters were hampered by exasperating delays in the collection of reports over the telegraph lines, especially in the international exchange of observations. Wireless telegraphy had been extensively used for gathering reports from vessels and supplying vessels with forecasts, but not for the interchange of meteorological information on land. The war changed all this. Radiotelegraphic weather messages became the rule, and the advantages of the new system were so obvious that the tendency has been to retain it as far as possible since the war.