We have already described at the beginning of this chapter the exact location of the salient that ran around Riga from Dubbeln on the Gulf of Riga by way of Mitau to Uexkuell on the Dvina. The first sector of it--Dubbeln-Mitau--was approximately twenty-five miles long, and the second--Mitau-Uexkuell--about thirty miles. On its western and northwestern side it was bounded to a great extent by the River Aa and by the eastern half of Lake Babit. The latter is about ten miles long, but only a little more than one mile in width and runs almost parallel to part of the south shore of the Gulf of Riga, at a distance of about three miles. On its southern and southeastern sides the salient followed, for some ten miles, first the post road and then the railroad from Mitau to Kreutzburg on the Dvina--about fifty miles northwest of Dvinsk--and then turned to the northeast for another twenty miles or so. On this latter stretch it crossed two tributaries of the River Aa, the Eckau and the Misse. Through the entire depth of the salient, in a southwesterly direction from Riga, runs a section about twenty-five miles long of the Riga-Mitau-Libau railroad, cutting it practically into two equal parts. Another railroad connects Riga with Dubbeln and still another with Uexkuell, so that the Russians had good railroad communications to every point of the salient. The inside of the latter, besides the rivers mentioned, contained some half dozen other smaller waterways, tributaries of the Aa and Dvina, and was covered almost entirely with dense forests. In the center of these there are located extensive swamps known as the Tirul Marshes, and smaller stretches of swamp lands are also found in various other sections of these woods. With the exception of the Mitau-Riga railroad there are only two means of approaching Riga, a fairly good road that leads along Lake Babit from the Aa to Riga, and another that runs from Gross Eckau on the Eckau River through the woods by way of Kekkau to Riga and in its northern part parallels the Dvina. The latter stream widens considerably about ten or fifteen miles above Riga and forms many small islands, the largest of which is Dalen Island, just to the north of Kekkau. Separating it from the mainland is only a comparatively narrow arm of the Dvina. The northern tip of the island is solid, somewhat elevated ground, and commands the eastern main arm of the Dvina as well as its eastern bank. If the Germans could gain this island their chances of reaching Riga from the south would be many times increased. An attack in that direction had nothing to fear from a flanking movement on the part of the Russians, because the latter would be prevented from getting at their advancing enemy either from the west or northwest by the impassable Tirul Marshes.