Why the Russian offensive failed is not a question with a "one-shot" answer. Like most history, it is complex and yet simple. Battles are lost or won because of basics, or lack of them. This battle is no different. The Russians began with a faulty plan, a lack of supplies, and poor leadership; added to this was the problems of topography, ffne leadership on the part of the enemy, and enemy knowledge of their orders. These factors spelled not only defeat, but also disaster for the Russians.

Chief Fault

The chief fault lies in the original plan of 1910. The Russians failed to concentrate in force against either the Austrians or the Germans. Their efforts were divided between two stools, and both offensives suffered from a lack of a "knock-out punch." The error was compounded in the division of forces in the East Prussian campaign. Neither army, both on the advance, was able to supply the force necessary for a superiority over the Eighth Army. Thus, they were subject to be destroyed singly. Since only the regular army was involved in the campaign, it was the elite of the Russians who were lost, making a later expansion of the army impossible.

The armies suffered, in the advance, from a lack of supplies. Both armies advanced before their supply trains were ready. After Gumbinnen, Rennenkampf was forced to halt due to lack of supplies, making Samsonov's position precarious. Neither army could use the railroads for supply, due to the difference in gauge. (The Russians had a broader gauge.) In the case of the Second Army, supplies could not even be sent by railroad to the frontier, because there were no lines there at all.

Both of these deficiencies were there to halt any invasion. Since the plan was offensive, this was a major oversight by the Russians.

Topography

The topography of East Prussia favored the defensive. Due to the positioning of the roads, the attacker was forced to advance in column over a wide front. This meant that each corps was forced to act independently, and the reinforcement of a threatened sector was difficult, if not impossible, due to the scarcity of lateral communication.

The role of the Masurian Lakes and the chain of fortresses between them cannot be minimized. Neither army could directly support the other, and it was impossible to concentrate into an overwhelming body until they were both west of the lakes. The lakes dictated the type of offensive necessary; to ignore them would be to invite a flank attack.

The knowledge the Germans had of the Russian code and orders was invaluable; without it the battle of Tannenburg would have been far less the victory it was. Since a mass army needs some form of radio communication, it is all but impossible to believe that more qualified radio operators could not have been available -- at least some that could have kept the code a secret.

Whereas the Germans knew Russian intentions, the opposite was true of the Russians. This was due, greatly, to the lack of effective use of the cavalry by the Russians. They had eight cavalry divisions, compared to one for the Germans. Not only did the Russian Cavalry fail to find the Germans, it also failed to mask the Russian movements from the Germans. Even without the intercepted messages, the Germans had a fine knowledge of Russian movements.

Even though a Russian victory in East Prussia would not have brought the war to a conclusion, we believe that one could have been achieved. The Russian Plan had called for the deployment of 30 divisions against the Germans. Since the Russians desired to clear East Prussia, we believe a total destruction of the German army, east of the Vistula, would not be necessary. The objective of the campaign would be a preliminary to an assault on Berlin.

The northern army, because it could be supplied (at least by railroad to the border), is the larger of the forces, 18 divisions. Its objective would be to advance north of the lakes and cut off Konigsberg from the main Russian force. Opposite the lakes would be a two division covering force. South of the lakes, near the border, would be smaller force, 6 divisions. It would be on the tactical defensive, guarding against an offensive against Warsaw. West of Grodno, you'd find the reserve of 4 divisions, able to intervene in an offensive against either the southem group or those forces covering the lakes.

After forcing the main German army from Konigsberg, 3 divisions would be left as a covering force. The southem group and the main body of the northem group then would march toward each other west of the Masurian Lakes. The reserve beginning to move up, would follow the path of the northern group. The combined force of the northem and the southern group (minus 2 divisions to watch the forces west of the lakes), 19 divisions with 4 more following, then would move westward. They then would be able to reach the line Danzig-Thom with 18-20 divisions (the remainder left behind to cover fortresses, guard lines of supply, etc.), where they'd unite with late-formed Tenth Army south of Thorn.

Any German offensive against the weak southern group would result in a retreat by that force. The northern force could handle any German attack. The two, when combined, should be strong enough to continue the advance. If possible, heavy artillery could be moved up to break through Lotzen and free more Russian divisions after the two groups had united west of the lakes. Reserves from the interior should be added to the forces covering Konigsberg, making it into a formal sedge. The heavy artillery, after its use on Lotzen, should be sent there.

This plan is of limited intent, perhaps unacceptable to the Russians in 1914. But, by mid to late September, the Russians could have had 30-35 divisions on or across the Vistula. With the northern flank secure, an advance on Berlin could be contemplated. Perhaps, by this method, the war could have been won in the east, by the Russians, that is!

More Anatomy of a Failure

Russian Invasion 1914
Analysis
Russian and German Losses
Large Maps Tannenburg and Masurian Lakes (very slow: 319K)
Jumbo Maps Tannenburg and Masurian Lakes (extremely slow: 711K)