Captured flying officers accused of distributing propaganda were tried in Germany by court martial and received severe sentences. Although in fact the sentences were not carried out, after negotiations had taken place through a neutral Power between the British and German Governments, the Germans let it be known that any future cases would be treated with the utmost severity. The French continued the use of aeroplanes in spite of this threat. But the British Air Ministry opposed the use of aeroplanes, partly on the ground of the “bad psychological effect of working under such threats, on young pilots and aviators,” and partly on the more valid ground that the supply of trained men and of machines was no more than sufficient for the direct purposes of this branch of the forces. After an attempt, obviously impractical, to distinguish between propaganda that could not be regarded as “inflammatory” and that therefore could be distributed by aeroplanes, and propaganda that could not escape this charge, British G.H.Q. accepted the position and decided against the use of aeroplanes for the distribution of literature. The stock of literature prepared for the western front, except such small parts of it as could be used by other army devices, was transferred to the Ministry of Information and to the French army.
The War Office Enemy Propaganda Section then turned to the devising of other possible methods for the distribution of literature by mechanical means. Information was collected from all possible sources, the methods of the enemy being carefully watched. With the assistance of the Aerial Inventions Board and the Munitions Inventions Department, many devices were tried, and as soon as any had reached a promising stage, the officer in charge took it out to France, to discuss its possibilities, and, with the assistance of the intelligence officers of the army, to test it under field conditions.
A section of G.H.Q. Intelligence had obtained great success in dropping homing pigeons and other means of carrying messages on known areas where they could be found by British agents behind the enemy lines. In this work fabric balloons with timing devices for dropping loads at the required localities were employed, but the apparatus on the one hand was unnecessarily exact, and, on the other, much too costly for the distribution of literature. The Germans were found to be using very large balloons of scarlet Japanese paper which carried bundles of newspapers and other matter long distances, sometimes releasing them by slow-burning tinder fuzes. It was clear, however, that this method was haphazard, as balloons and loads destined for the neighbourhood of Verdun not infrequently dropped in Kent. Experiments were undertaken to study the lifting capacity of light balloons, the load and degree of filling that would enable them to rise to an approximately known height, and the arrangement of time fuzes so that they would liberate weights at known distances varying with the strength of the wind. At the same time experiments were made as to the shape, economical mode of manufacture and dimensions of paper balloons, and on the treatment of the paper to lower the rate of diffusion of coal-gas or hydrogen.
A large number of devices such as rockets, grenades and shells were enquired into, but were not adopted because of various objections raised against their use by the military authorities. A device consisting of a fire-balloon, the fabric of which consisted of propaganda sheets joined by strips of touch paper, seemed promising, but did not reach success.
Extensive experiments were carried out with the object of adapting an apparatus invented to distribute light bombs to the distribution of literature. It consisted of a box-kite with an automatic conveyer which carried five-pound loads of propaganda up the cable, liberated them at the required height, and automatically returned for another load, the sheets when liberated being carried to their destination by the wind. The method was extremely good; it was cheap, easy to work, and had a range of upwards of ten miles according to the strength of the wind. But objection to its use at the front was taken by the Air Force on the ground that the cable of the kite would be a danger to aeroplanes.
In connexion with the last-mentioned apparatus, extensive observations were carried out on the wind-driftage of sheets of paper of different shapes and weights, and of the methods of releasing them at height. Experiments were made from aeroplanes and from captive balloons, and the range and conditions of falling were ascertained. It was found, for example, that in a wind of approximately ten miles an hour, a bundle of 150 sheets liberated at a height of 2,500 ft., came to the ground two miles away, scattered over an area 500 yd. square. In higher winds and from greater heights much more distant ranges could be attained. The War Office Propaganda Section accordingly suggested that aeroplanes might be safely used, flying at heights proportioned to the strength of the wind, and the distance of the enemy lines, by flights well within the British lines. But this proposal also was “turned down.”
By the end of 1917 it became clear that the use of paper balloons was the only method which would encounter no opposition, and attention was therefore concentrated on producing them on a large scale and on applying the experience gained in other directions to them. By far the largest bulk of propaganda distributed by the Allies on the western front was released from balloons, and it may therefore be of historical interest to describe their final form. The propaganda balloons were made of paper cut in longitudinal panels, with a neck of oiled silk about 18 in. long. Their circumference was approximately 20 ft. and their height when inflated 8 feet. They were liberated inflated nearly to their full capacity—from 90 to 95 cub. ft. of hydrogen. The weight of the balloon was under one pound, the load of propaganda four pounds. The leaflets were attached to a fuze of treated cotton, similar to the tinder of flint pipe-lighters, and burning at the rate of an inch in five minutes. The string of propaganda was tied to the neck of the balloon, and just before liberation a slit was cut in the neck to permit the escape of gas, and the end of the fuze was lighted. The weight and lift were adjusted so that the balloon could rise several thousand feet into the air before the loss of gas due to expansion would have caused a state of equilibrium. At this point the first bundle of leaflets was set free, and the process was continued until, at the end of the run, the last bundle was released. The total time length of the fuze and the attachment of the bundles to it were calculated according to the area which it was desired to reach and the strength of the wind. Experimental improvement of the “dope,” by which the rate of diffusion of the gas was lowered, and the manufacture of balloons of double the standard capacity, had made runs of upwards of 150 m. practical, before the Armistice suspended operations. But the bulk of the propaganda was actually scattered over an area of from 10 to 50 m. behind the enemy lines, rest camps and villages occupied by the troops being made the chief targets. Each distribution unit at the front consisted of two motor lorries which carried the balloons, hydrogen cylinders, and personnel to convenient positions, generally from 3 to 4 m. behind the front line.
Early in March 1918, the method of balloon distribution was in full working order, and the War Office Propaganda Section resumed the active preparation of material. The reproduction of selected letters written by prisoners of war was resumed, and Le Courrier de l'Air was enlarged and improved by the introduction of direct propaganda. A series of leaflets, known as the A.P. (Aerial Propaganda) was begun. The first of these, sent to France in March, was a complete German edition of the British Prime Minister's speech on British War Aims. This had been incompletely reported in the German newspapers, and in the new edition attention was directed to the portions which had been taken out by the German censorship; copy for other leaflets was selected from German and Austrian newspapers, was contributed by G.H.Q. (France), by the War Aims Committee, by the Ministry of Information, and by the new Directorate of Propaganda in Enemy Countries which had been established under Lord Northcliffe. But the whole series was selected, revised, edited, and produced by the War Office, and a very large proportion of the actual leaflets were prepared by the officer-in-charge. The first of the series was sent to France on
