To give a better idea of the work imposed on the Belgian Army it will be convenient to summarise what, in the present war, is implied by organising the defences of a sector. The power of modern artillery and explosives, which are able to destroy the most massive fortifications, renders it impossible to rest content with a single position, however strong it may be. Hence the absolute necessity for extending the state of defence to a _deep zone_ and for creating _several successive positions_. This is the only way of localising a temporary success, such as the enemy may win at any time if he take the necessary steps and be willing to pay a heavy price for it. Moreover, every position must itself consist of a series of defensive lines, a short distance apart, each covered by its own subsidiary defences. These conditions are all the more difficult to fulfil when the defences are rendered less permanent by the nature of the ground, as is the case on the Belgian front, where one cannot burrow into soil which is practically at sea level. It thus comes about that--to take an example--the organised zone, 10 to 12 kilometres deep, between the two natural defensive lines of the Yser and the Loo canal, is nothing more than an unbroken series of organised lines, placing as many successive obstacles in the path of an assailant who may have succeeded in breaking through at any point. The positions nearest to the enemy are necessarily continuous; and the lie of each is influenced not merely by the terrain but still more by the arbitrary direction of the contact lines of the two opponents. Each line, therefore, follows a twisting course. More or less straight stretches are succeeded by salients and re-entrant angles which take the most varied forms. The defences embrace farms and other premises and small woods, all converted into _points d'appui_. Where such are lacking at important points, they must be created artificially. Communication trenches, allowing movement out of sight of the enemy, connect the various positions, and the successive lines of a position, with one another. Shelters have to be constructed everywhere--they cannot be built too strong, to protect the men as much as possible from bombardment and from the weather during their long spells on guard in the trenches. Special emplacements must be most carefully prepared for machine-guns, bomb-throwers and trench-mortars, which play a part too important to need special comment. The whole zone is dotted over at various distances from the enemy with batteries, or emplacements for batteries, of all calibres. You will understand that their construction represents a vast amount of hard and exact work, and that only with the greatest difficulty can they be more or less satisfactorily hidden from the enemy's direct or aerial observation in a plain that is practically bare and commanded everywhere by the Clercken heights.