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REPORT OF COMMISSION VII 69 
battle zone, and through a comparison with photos of the same area, which were 
perhaps taken earlier, the tactical photo-interpretation is intended to give 
exhaustive intelligence about terrain, details in the enemy fortifications, the 
position of artillery and the grouping and position of reserves, and certain facts 
for estimating the probable plan of action of the enemy, etc. 
The interpretation permits, partly to establish objectively which details of 
military importance, etc. are visible in the photos, and partly to estimate the 
inner tactical connection between these details. 
The first mentioned task means that the photos must be systematically 
examined over their whole surfaces. This work is of a technical nature, and can 
be done by personnel lacking higher tactical schooling. On the other hand it is 
necessary to have knowledge of the details of the enemy's field fortification 
technique, artillery and different types of vehicles, etc. The training of this cate- 
gory of personnel in elementary photo-interpretation, aims at reducing the time 
for this kind of work to a minimum. See the discussion under ‘TEACHING,’ 
The other task—estimating the inner tactical connection between details 
already established—places great demands on both the tactical and technical 
knowledge of the interpreter. He must be well acquainted with the tactics of the 
enemy and the situation in question, besides knowing the results of other recon- 
naissance resources. 
'The systematic examination and the tactical estimation are closely related. 
Therefore, photo-interpretation is usually done by the leader dividing the detail 
work among his collaborators, but interpreting the photos himself, using the 
tactics of the enemy as a guide. 
If, for example, the interpretation is of a defense position, he carries out his 
own interpretation as follows: He always starts by a careful study of the ter- 
rain. Through stereoscopic photo reading he acquires a clear conception of the 
height circumstances, the nature of the ground and to what degree it is passable, 
how the terrain is covered (by woods, etc.), its surveyability, the system of roads, 
paths and beaten tracks, etc. With the guidance of these facts and knowledge of 
the enemy tactics, certain conclusions may usually be drawn regarding the 
probable general plans of the enemy. With these in mind, he then studies the 
direction of the barbed wire belts and anti-tank ditches, etc. which give good in- 
telligence of the general direction and strength of the enemy's positions. After 
this, other fortification constructions are established in connection with the 
obstacle lines, the positions of heavy artillery together with the probable direc- 
tions of flanking weapons and tasks, etc. Obvious gaps in the system of em- 
placement are studied very carefully, from which it is often possible to give 
the approximate position of such single flanking weapons, which (thanks to 
a well chosen position and clever camouflage) have not been detected in the 
photos, but which, in consideration of the system of emplacements, most 
probably exist. 
After the system of emplacements and the defense of the first line have thus 
been established, the interpretation continues in depth into the lines of defense. 
The grouping of artillery, and positions of mortars, etc. are established. All 
tracks and civilian roads which do not appear to have a definite purpose are 
followed, and their ends or forks are studied very carefully. Finally he tries to 
detect the positions of the reserves, prepared directions of counter attacks and 
camp areas. At the same time he tries to form a conception of the tasks of the 
individual defense constructions, and also of the probable battle plan. 
The results arrived at by the leader and his collaborators flow together dur- 
ing their work, to form an interpretation which embraces not only the details 
detected, but even their certain, or presumed inner connection. From the report,