the three central corps (XIII., XV., XXIII.) was General von
Scholtz with his XX. Corps and part of a force of Landwehr,
Ersatz and Landsturm, which had been taken out of the fortresses
of Graudenz and Thorn to watch the line of the frontier W. of
Soldau. Opposite the Russian VI. Corps on the Ortelsburg side,
and holding the lake barrier, there were other German forces of
the same kind.
The first efforts of the German command were directed to forming an attack-mass on the basis of the XX. Corps. This mass would have to be taken from the forces confronting Rennenkampf, and released in succession according to the activity displayed from day to day - by him. Meanwhile, Scholtz's mission was to maintain an intact front on the wings of which these other forces, of greater or less strength, would come up for the enveloping effort. On the right or W. wing these forces consisted of the I. Corps (von Francois), which, after Gumbinnen, had been entrained for stations near the Vistula but then had its transport switched to the region at and E. of Deutsch Eylau, and of such Landwehr and Ersatz as could be assembled at the E. end of the frontier cordon. On the other flank, there were successively drawn off from Rennenkampf's front the 3rd Res. Div., the I. Res. Corps (von Below), the XVII. Corps (von Mackensen), and the 6th Landwehr Bde. from the Lotzen area, the defence of Lb'tzen being left to its Landsturm garrison, the defence of Konigsberg to its mobile reserve posted on the Deime, and the observation of Ren- nenkampf's army to two cavalry brigades. But between Aug. 23-6, the dates at which the offensive was to begin, the 3rd Res. Div., part of the frontier Landwehr and Ersatz forces, and even the first units of the I. Corps which entrained, were involved in the fighting of the XX. Corps, which had to sustain the weight of Samsonov's attack, particularly at Orlau and Lahna on Aug. 23.
On the night of Aug. 25, Below (I. Res. Corps), after cross- country movements imposed by the crowding of main roads with refugees, had reached Seeburg; the 6th Landwehr Bde., Lautern ; Mackensen (in one long march) , Bischof stein. Von Scholtz with his XX. Corps and attached formations held the line Kosten Forest (exclusive)-Gilgenburg-Hohenstein (inclusive); von Francois (I. Corps) was detraining at various stations around Deutsch Eylau and forming up on the line Tuschau-Kielpin; while Muhlmann's detachment of the Landwehr and Ersatz forces had driven hostile cavalry out of Strassburg and Lauten- burg, and was ready to cooperate from Lautenburg eastward. In a day or two the catalogue of available German forces was to be completed by the arrival at Allenstein of von der Goltz's Landwehr div. from Schleswig-Holstein. On the Russian side, while the I. Corps hung back, as ordered, in echelon on the left, and the XXIII. and XV. swung up in pursuit of von Scholtz from the E.-W. line facing Gilgenburg-Lahna to a N.N.E.- S.S.W. line facing Gilg'enburg-Hohenstein, the XIII. Corps was advancing northward on Allenstein, and the right echelon (VI. Corps and 4th Cav. Div.) from Ortelsburg had reached Bischofs- burg. Rennenkampf meanwhile reached the line Insterburg- Angerburg and his left corps was approaching the eastern lake barrier. But liaison between Rennenkampf and Samsonov, and their common superior Zhilinsky, was already, as it remained to the end, imperfect; and even within the II. Army itself the various corps maintained only intermittent touch with head- quarters by wireless (sent en clair), and casual communication by motor-car and aircraft.
On the morning of Aug. 26 the battle opened at all points. In the centre, the Russian XV. Corps drove the 3rd Res. Div. into the woods to the W. of Hohenstein, but von Unger's Landwehr and Ersatz were hurried up from the southern frontier guard and, posted behind the barrier of the Drewenz at Mtihlen, prevented a roll-up of the XX. Corps' left, while the 3rd Res. Div. rallied under cover of the woods. Thus the XX. Corps was enabled not only to hold on in front of Tannenberg against the Russian XXIII. Corps and part of the I. Corps, but to open an attack which brought its centre to Ganshorn and Thurau. Farther S. the German I. Corps, the principal element on which
the projected " Cannae " depended, had not made the progress expected by Hindenburg. Its detrainment was not complete, and von Francois attempted to obtain a postponement of the attack; after some discussion, Ludendorff insisted that the corps should begin its attack at noon, and it did so at i P.M. But at that time it was too late to capture the heights of Usdau- Gross Tauersee as had been intended. Meantime Miihlmann, holding Strassburg and Lautenburg against the Russian 6th and i sth Cav. Divs., though he could not prevent an inroad, between these points, on the rear of von Francois's assembly area pulled out his main body eastward to Heinrichsdorf, the capture of this point bringing him into line with von Francois.
In sum, the left of von Scholtz's forces was already bent back (though in no wise enveloped) by the Russians, and the German enveloping wing under von Francois was only at the beginning, instead of in the middle, of its task. From the point of view of Hindenburg's headquarters, this was not a satisfactory opening to a battle fought against time. But events on his left wing on Aug. 26 gave a new turn to affairs. The Russian XIII. Corps, approaching Allenstein, met with no opposition, and the VI. Corps, heading N. and seeking for liaison with Rennenkampf, suffered disaster. The latter had pushed its leading division as far N. as Gross Bossau, where it halted and entrenched. In this position it was found and attacked by Mackensen's XVII. Corps, while the 6th Landwehr Bde. and part of the 36th Res. Div. of Below's I. Res. Corps, N. of Lake Lautern, came in upon its rear. At .nightfall it was broken by a charge of the Landwehr, and fled in disorder, seriously impairing the moral of the following division. Meanwhile the remainder of the German I. Res. Corps moved on Wartenburg. Thus, the Russians' extreme right was in rapid retreat, while their centre was advancing northward, and the Germans saw that the opportunity of double envelop- ment was not gone by, but only maturing. Accordingly, on the evening of Aug. 26, von Francois was ordered to attack the Usdau-Gross Tauersee position at dawn with the utmost energy, Miihlmann to push on from Heinrichsdorf on Borchersdorf. This achieved, the I. Corps was to advance as rapidly as possible on Neidenburg, flank-guarded to the S. by Miihlmann. Von Scholtz was to continue the attack of his centre eastward so as to cut off all Russian troops north of Gross Gardienen, while his right intervened in the battle at Usdau and his left held on at Miihlen and on the Drewenz. Mackensen was to pursue the beaten Russians due S. on Ortelsburg, while the movements of Below (whose ist Res. Div. was already due E. of Wartenburg) and of von der Goltz (whose Landwehr Div. was to begin detrainment Aug. 27, E. of Osterode) were apparently left to their own discretion, since headquarters intended to trust themselves on Aug. 27 entirely to von Francois and von Scholtz.
On Aug. 27 was fought the battle of Usdau. Here the German I. Corps, well in hand and complete, and aided on its left by the right of the XX. (Schmettau's detachment) and on its right by Miihlmann, completely broke the Russian resistance. But whether through tactical accidents, or a misinterpretation of orders, or desire to obtain elbow-room to the southward, the I. Corps, instead of driving due eastward from the captured line, wheeled to its right, pushing the Russian I. Corps on to Soldau, and itself reaching at nightfall the E.-W. line Heinrichsdorf- Borchersdorf-Schonwiese. The XX. Corps (less Schmettau's detachment) drove on in the centre, and reached a N.-S. line from the E. end of the Miihlen See to Skottau, facing a new Russian position at Waplitz, where their XXIII. Corps, and also part of the force defeated at Usdau, rallied. Meantime there had been critical fighting farther north. West of the line Hohenstein- Paulsgut the Landwehr and Ersatz of Unger and the 3rd Res. Div. were heavily attacked by the Russian XV. Corps, and Allenstein, undefended, was occupied by the Russian XIII. Corps. At the German headquarters it was rumoured that Unger's line had been broken, and the 37th Div. was hurriedly taken from von Scholtz's advancing line and put in on the Drewenz, to prevent a break-through towards Osterode.
Such a break-through with the aid of the fresh XIII. Corps from Allenstein (which could hardly be held up for long by von
