It will thus be seen that from the very start of their manoeuvre the Germans had succeeded in out-generalling Rennenkampf. On the left of their line they were containing four Russian divisions with garrison troops, equivalent to about a division. In the centre they were opposing eight divisions to seven Russian divisions. On the right they were advancing with no less than five divisions and two cavalry divisions against a single Russian division.
German Attack.—Goltz attacked and took Miawa on Sept. 4, and thereafter kept in check any of the units of the Russian II.
Army which attempted to advance. By the night of Sept. 5 Francois was approaching the southern end of the lakes. By the 6th he had taken Johannisburg and Nikolaiken, driving back the few Russian troops opposing him. By the 7th he was through the lakes and had captured Bialla and Arys. The Russian troops opposing him had been hurried up without proper artillery sup port and were dispersed in disorder. Eleven Russian battalions were thus dissipated without result. On the 8th Francois turned northwards against the Russian flank. Sept. 9 was to be a fateful day for the Germans. Mackensen had commenced his crossing at LOtzen during the 8th, but he could not enlarge the bridge-head.
His troops attacked at 5 A.M., 12 noon and 8 P.M. on this day without success and that evening he reported no progress to Francois.
Francois' attack against Soltmahnen on the morning of the 9th came as a complete surprise to the left flank of the Russians opposing Mackensen. By noon the Russians were in hopeless rout, leaving 5,00o prisoners and 6o guns in the hands of Francois. The German enveloping movement had met with complete success. Rennenkampf's left flank division had been destroyed and about 8,000 men of the Russian X. Army concentrating about Augus t6wo and Osowiec had been placed out of action. The left flank of Rennenkampf's army now lay open to the attack of five Ger man divisions. A second Tannenberg seemed more than probable.
Ludendorff had employed the 5th, 6th and 7th in bringing his eight divisions in line facing the Insterburg gap and, on the 8th, contact was gained with Rennenkampf's outposts. On the 9th, coinciding with Francois' attack, the Germans moved forward along the whole front. Little progress was made anywhere, and
on the right the Russians made a determined counter-attack which completely held up the German advance. This check seems to have paralyzed Ludendorff temporarily, for he ordered his right under Francois and Mackensen to hold fast and even to close in to the centre for fear of disaster. But Rennenkampf had taken fright at the menace to his left and had decided to withdraw. That night he ordered a general retreat. He had been just too quick for the Germans. When Ludendorff allowed his right to move forward again, nothing further than cutting off the streams of disorganized transport and breaking up the Russian rear-guards was possible. Rennenkampf had pushed his retreat with despera tion. Two of his corps had covered 58 m. in 6o hours. By the 13th he was safe from annihilation, and by the 14th his exhausted troops had crossed the East Prussian frontier between the forest of Rominten and the river Niemen.
Although the Russian I. Army had not been surrounded, it had suffered almost as much as the II. Army. Casualties since Sept. 6 had amounted to 12 5,00o men and 1 so guns. Two corps had been destroyed and the whole army was out of action as a mobile force through lack of transport. The chief credit for this success must lie with Francois. In his march round the southern end of the lakes his men had covered 77 m. in the four critical days Sept. 6-9, and there had been severe fighting on two of those days. Had Ludendorff been quicker to realise that Rennenkampf's counter-attack on the 9th was made in order to disengage himself, and had his orders to Francois for the loth and r I th not been so cautious, there can be no doubt that Rennenkampf's army would have been all but destroyed.
During their 28 days' invasion of East Prussia the Russians had lost some 310,000 men from the flower of their army and 65o guns. Their offensive had been completely defeated and they had been thrown on the defensive. It was not till late in the winter of 1914-15 that they began to show signs of activity once more. From the German point of view it was important to pre vent another Russian invasion of East Prussia and it was there fore decided to upset the Russian plans by a strong offensive.