Before the business of putting the ground in a proper state of defence could be initiated, the inundation had to be got under effectual control. This implied, let us note, the power to flood the ground on the enemy's side at will, while preventing the water passing beyond a sharply defined line, and making it quite impossible for the enemy to threaten us in turn. The enormous technical difficulties which our engineers had to overcome can easily be imagined. We may observe, in the first place, that the Yser district is intersected by many small tributaries of the river and by a number of interconnected canals. The two zones--our own and that of the enemy--thus had direct communication with one another, so that, unless minute precautions were taken, and a great deal of work done, it was not possible to flood either zone without exposing the other to a similar fate. [Illustration: AN ARTILLERY UNIT'S CONTROL POST] [Illustration: BATTALION HEADQUARTERS IN THE FRONT LINE] [Illustration: A SHELTER] [Illustration: A FOOTBRIDGE ACROSS THE FLOODS _From the First Line to an Outpost_.] [Illustration: VIEW OF THE FIRST LINE _Where it crosses Flooded Ground_.] [Illustration: FIRST-LINE TRENCH ROUND THE RUINS OF A FARM _Note the arch-shaped Traverses for protecting its Occupants from Snipers._] [Illustration: ADVANCED POST ON THE RIGHT BANK OF THE YSER _Beyond it is seen "No Man's Land."_] Nor was this all. The enemy was, and still is, at liberty to lower the water level by "bleeding" the inundation on his side. To defeat such attempts, it was necessary to put ourselves in a position to turn the requisite volume of water towards his lines. Finally, provision must be made for draining off the water promptly and carefully, should the need arise, so as to prevent a disaster being caused by the enemy increasing the inundation, or merely by the torrential rain which falls at times with disheartening persistence in this depressing region. A constant struggle between the two opponents was thus always in progress. Let us say at once that the ingenuity and unwearying exertions of our men always triumphed in contests of this kind. They continue to dominate the situation completely, and the Germans have had to own themselves beaten. The reader will realise that we cannot give a detailed description of the measures taken; the most difficult and complicated of which were unquestionably those designed to protect the Belgian lines from inundations let loose on the enemy's positions. It has been mentioned more than once that, thanks to their command of Nieuport and its locks, the Belgians held the key of the inundations in their hands. But we must not forget that for three years German shells have been continually directed at the locks and bridges. The works that have had to be undertaken, carried out and maintained in good condition throughout this region will astonish the experts when it is possible to reveal their real character.