Kovno's garrison attempted on that day another unsuccessful sortie, resulting in the capture of 100 men and in slight gains on the part of the besieging forces. The latter success was also repeated before Novo Georgievsk. By this time the general retreat, and the ever-increasing pressure on the part of the advancing enemy made itself felt even in the most northern part of the Russian line. There, as well as in the farthest south of the line, the least changes took place. But on August 15, 1915, German troops attacked the Russians near Kupishky, at the point where the original Russian front turned toward the southwest, and threw them back successfully in a northeasterly direction, capturing at the same time some 2,000 officers and men. August 17, 1915, marks the beginning of the end for Kovno and Novo Georgievsk. On that day both of these fortresses lost some of their outlying forts, and before Kovno alone 4,500 Russians and over 200 guns fell into the hands of the Germans. During the night of August 18, 1915, Kovno fell, after having been defended most valiantly against the ever-repeated attacks on the part of the Germans under General von Eichhorn. It was one of the strongest Russian fortresses, with eleven outlying forts on both sides of the Niemen, commanding this river at the point where it turns from its northerly course toward the west and defending the approach to Vilna from the west. Over 400 guns and vast quantities of supplies and equipment as well as about 4,000 officers and men made up the booty. On the same day additional forts of Novo Georgievsk fell, although the fortress itself still held out. The fall of Kovno, expected and discounted as it undoubtedly was by the Russians, was a serious blow. It now became absolutely necessary to withdraw all their forces in that sector beyond the Niemen, in order to avoid their being cut off by German columns advancing from Kovno to the south along the east bank of the Niemen. This need found expression in the immediate withdrawal of the Russians from the line Kalvarya-Suvalki. For the Germans an additional advantage arose in their ability to establish contact between Von Hindenburg's forces in Poland and Von Buelow's army in Courland and thereby remove all possibility of having the latter's right wing enveloped.