The Russian commander, Samsonoff, with his army running from Allenstein southwards, was facing towards the west. He had with him perhaps 200,000 men, perhaps a trifle less. His reconnaissance was faulty, partly because the aeroplanes could discover little in that wooded country, partly because the Staff work was imperfect, and his Intelligence Department not well informed by his cavalry patrols. He thought he had against him to the west only weak forces. As a fact, the Germans were sending against him what they themselves admit to be 150,000 men, and what were quite possibly nearer 200,000, for they had drawn largely upon the troops within Germany. They had brought round by sea many of the troops shut up in Königsberg, and they had brought up the garrisons upon the Vistula. Further, they possessed, drawn from these garrisons, a great superiority in that arm which throughout all the earlier part of the great war was the German stand-by—heavy artillery, and big howitzers capable of use in the field.
On Wednesday, 26th August, Samsonoff first discovered that he had a formidable force in front of him.
It was under the command of von Hindenburg, a man who had studied this district very thoroughly, and who, apart from his advantage in heavy artillery, knew that difficult country infinitely better than his opponents. During the Wednesday, the 26th, Hindenburg stood upon the defensive, Samsonoff attacking him upon the line Allenstein-Soldau. At the end of that defensive, the attack on which was badly hampered in so difficult a country, von Hindenburg massed men upon his right near Soldau. This move had two objects: first, by pushing the Russians back there to make them lose the only good road and railway by which they could retire south upon their communications into the country whence they had come; secondly, to make them think, in their natural anxiety for those communications, that his main effort would be delivered there to the south. As a fact, it was his intention to act elsewhere. But the effect of his pressure along the arrow a was to give the Russian line by the evening of that Wednesday, the 26th of August, the form of the line 1 upon Sketch 73.
The advantage he had thus gained in front of Soldau, Hindenburg maintained by rapid and successful entrenchment; and the next day, Thursday, 27th August, he moved great numbers round by railway to his left near Allenstein, and appeared there with a great local superiority in numbers and in heavy guns. By the evening of that day, then, the 27th, he had got the Russian line into the position 2, and the chief effort was being directed along the arrow b. On the 28th and 29th the pressure continued, and increased here upon the north; the Russian right was pushed back upon Passenheim, for which there was a most furious fight; and by the evening of the 29th Samsonoff's whole body was bent right round into the curve of the line 3, and vigorous blows were being dealt against it along the arrow c, which bent it farther and farther in.
It was clearly evident by that evening, the 29th of August, that Samsonoff must retreat; but his opportunities for such a retreat were already difficult. All he had behind him was the worst piece in the whole country—the triangle Passenheim-Ortelsberg-Niedenberg—and his main avenue of escape was a defile between the lake which the railway at Ortelsberg uses.
His retirement became hopelessly congested. Further pressure along the arrow d, during the 30th and 31st, broke that retirement into two halves, one half (as at 5) making off eastwards, the other half (as at 4) bunched together in a hopeless welter in a country where every egress was blocked by swamp and mire, and subjected to the pounding of the now concentrated ring of heavy guns. The body at 5 got away in the course of the 1st and 2nd of September, but only at the expense of leaving behind them great numbers of guns, wounded, and stragglers. The body at 4 was, in the military sense of the word, "annihilated." It numbered at least two army corps, or 80,000 men, and of these it is probable that 50,000 fell into the hands of the enemy, wounded and unwounded. The remainder, representing the killed, and the chance units that were able to break out, could hardly have been more than 20,000 to 30,000 men.
Such was the victory of Tannenberg—an immensely successful example of that enveloping movement which the Germans regarded as their peculiar inheritance; a victory in nature recalling Sedan, and upon a scale not inferior to that battle.
The news of that great triumph reached Berlin upon Sedan Day, at the very moment when the corresponding news from the West was that von Kluck had reached the gates of Paris, and had nothing in front of him but the broken and inferior armies of a disastrous defeat.