Any armies approaching from the south must cross the rivers Rupel and Nethe, which practically, in the shape of a semicircle, swing around the city to the south at a distance varying from about six to twelve miles. Within this circle of flowing water, and about two miles from the city, is another circle, formed by twelve powerful forts. At a point almost due east from the center of the city and commanding the railroad to Holland, by way of Turnhout, is located the first of eight forts, designated by numbers. From there they swing to the south and west, with fort eight very close to the Scheldt and directly south to the village of Hoboken. On the other side of the river are Forts de Cruibeke and Zwyndrecht, the latter commanding the railroad to Ghent. Further north and right on the banks of the Scheldt are Forts St. Marie, la Perle, and St. Philip, the first two on the left bank and the last on the right, all three opposite the new harbor and docks. In the northeast Fort de Merkem guards the railroad to Rotterdam. Outside of this circle and in the south, outside of the Nethe-Rupel line, there is another complete circle of nineteen even stronger forts, at a distance from the city varying between five and ten miles. Starting again in the east--due east from fort one--and swinging south, these forts are named: Oeleghem, Broeckem, Kessel, Lierre, Koningshoyckt, Wavre St. Catherine, Waelhem--the last two only a few miles north of Malines--Breendonck, Liezel, Bornem, Rupelmonde, Haesdonck, Doel, Blauwgaren--the last two guarding the Scheldt at the point of its entrance into Holland, one on each bank--Stabroek, Ertbrand, Brasschaet, Schooten, and Gravenwezel. Between these outer forts there were redoubts of considerable strength, which were armed with 4-inch guns. The forts of the inner ring are placed at regular intervals of 2,200 yards and at a distance of about 3,500 yards from the enceinte of the city, which itself had powerful defenses as well. [Illustration: LIEGE FORTS, SHOWING GERMAN ATTACK] [Illustration: SIEGE AND FALL OF ANTWERP] Add to these defenses the important fact that the entire district surrounding Antwerp was subject to inundation to such a depth that all approach to the city could be made impracticable to an enemy force with heavy cannon and ammunition. Military authorities held Antwerp to be of incomparable strength and as nearly impregnable as engineering genius could make it. During the latter part of September, 1914, several of the outer forts were subjected to bombardment, and many of these had become useless as defenses. General von Beseler's advance was still barred by the river Nethe, upon the opposite bank of which the defense was concentrated. During the engagements which now ensued the German aircraft kept the commanders advised as to conditions behind the enemy's lines, now and then dropping bombs, apparently doing considerable damage.