The Battle of Tannenberg was a decisive engagement between the Russian Empire and the German Empire in the first days of World War I, fought by the Russian First and Second Armies and the German Eighth Army between 23 August and 2 September 1914. The battle resulted in the almost complete destruction of the Russian Second Army. A series of follow-up battles destroyed the majority of the First Army as well, and kept the Russians off-balance until the spring of 1915. The battle is notable particularly for a number of rapid movements of complete corps by train, allowing the single German Army to present a single front to both Russian Armies.
Frustrating this plan was the Russians' lack of a quality railroad network. Additionally, the Russian trains operated on a different gauge than the Germans, meaning that unless the Russians acquired German railroad cars, most of their armies could only be brought as far as the German border. The presence of the armies of Austria-Hungary to the south as well as initially those of Japan to the east limited Russia's involvement in the beginning. Nevertheless, the Russians considered the Germans to be their primary threat, and had organized a plan to use limited forces to quickly seize East Prussia.
The Germans likewise, considered the Russians to be their primary threat. The entire Schlieffen Plan was based on the idea of defeating France and Britain as quickly as possible, and then transporting their armies by train to the eastern front. This allowed the Germans to garrison Prussia fairly lightly, with a single army, the Eighth, while the German Ninth Army was stationed in central Germany to reinforce either front. That said, there was little allowance for anything other than a delaying action while the outcome in the west was decided. In order to delay the Russian forces as long as possible, the entire area around Königsberg, near the Russian border, was heavily fortified with a long series of fieldworks.
Just prior to the opening of the war the situation developed largely as pre-war planning had expected. The German Eighth Army was in place southwest of Königsberg, while the two available Russian armies were located to the east and south, the latter in what was known as the "Polish Salient". Russian battle plans called for an immediate advance by the First Army under General Pavel von Rennenkampf into East Prussia, with Königsberg as their short-term goal. The Russian Second Army under General Alexander Samsonov, located to the south, was to move westward around the Masurian Lakes and then swing north over a hilly area to cut off the Germans, who would by this point be forced into defending the area around Königsberg. If executed successfully, the Germans would be surrounded.
Worried about his loss at Gumbinnen and the continued advance of the Russian Second Army from the south, Prittwitz ordered a retreat to the Vistula, effectively abandoning eastern Prussia. When he heard this, Helmuth von Moltke, the German Army Chief of Staff, recalled Prittwitz and his deputy Waldersee to Berlin. They were replaced by Paul von Hindenburg, called out of retirement, with Erich Ludendorff as his chief of staff.
Things were not quite as dire as they seemed to the German commanders in Berlin. The two Russian commanders, Samsonov and Rennenkampf, disliked each other after Samsonov had publicly complained about Rennenkampf's behavior at the Battle of Mukden in 1905. Although the common belief that the two generals had come to blows at a railway station has proved to be incorrect (Showalter, 1991, p.134), Rennenkampf would be disinclined to help Samsonov except under dire circumstances. Additionally, Samsonov's Second Army was having serious problems moving forward due to poor supply preparations, and unknown even to Samsonov, Rennenkampf had decided to delay the First Army's advance to regroup after Gumbinnen, believing the Germans were preparing another attack.
Nevertheless, the scale of the forces deployed still meant the Russians had the upper hand. As they were currently deployed, the German Eighth Army could not even cover the entire front along Samsonov's line of march, leaving Samsonov's left wing in the southwest open to advance with no opposition. Unless troops from the Königsberg area (I, XVII and I Reserve Corps) could be moved to check this advance, the Germans were in serious danger of being cut off.
In theory, the plan was extremely risky. If the First Army turned to the southwest instead of advancing directly westward towards Königsberg, they would appear on the Eighth Army's extreme left flank, allowing for either a counterattack against the Eighth, or alternately turn north towards Königsberg from the undefended south. However, Hoffmann was convinced of the soundness of his plan, both because he was aware of the animosity between the Russian generals, and also because of the Russian habit of transmitting their next day's marching orders over unencrypted radio communications. It appears the Russians had outrun their secure telegraph landlines, and were short of trained telegraph operators and cryptographic equipment. This forced them to transmit their messages in the clear, and these were easily intercepted and translated by the Germans.
When Hindenburg and Ludendorff arrived on 23 August, they immediately stopped the retreat and put Hoffmann's plan into action. Since Prittwitz had already ordered the German troops to pull back via train, Ludendorff directed I Corps to detrain near Deutsch-Eylau to cover the left flank of XX Corps, who had been in front of the Second Army since before the battle at Gumbinnen. Hoffmann had already issued similar orders, so little confusion resulted. The trap was being set.
Ludendorff also learned at this point that von Moltke had decided to take three corps and a cavalry division from the Western front and redeploy them to East Prussia. Ludendorff protested that they would arrive too late to have any effect, while at the same time weakening the German offensive through Belgium against France. However, von Moltke considered East Prussia too politically important to lose, and ignored Ludendorff's protests.
Starting on 22 August, Samsonov's forces had met the Germans all along his front, and had successfully pushed them back in several places. On the 23rd they attacked the German XX Corps, which retreated to the Orlau-Frankenau line that night. The Russians followed, and on the 24th they met them again at Orlau-Frankenau, where the now-entrenched XX Corps temporarily stopped the Russian advance. Once again XX Corps retreated in order to avoid possible encirclement by superior forces. Undeterred, Samsonov saw this as a wonderful opportunity to cut this unit off completely, because, as far as he was aware, both of his flanks were unopposed. He ordered most of his units to the northwest, towards the Vistula, leaving only his VI Corps to continue north towards their original objective of Seeburg.
Concerned about this possible flanking maneuver, Ludendorff issued an order to François' now-deployed I Corps to initiate the attack on Samsonov's left wing at Usdau on 25 August. François rejected this direct order, stating there was no way to have the corps ready in time and that he wanted to wait until his artillery support was ready on 27 August. Ludendorff and Hoffmann would have none of this, and traveled to meet François to repeat the order in person. François agreed to commence the attack, but complained of a lack of artillery shells.
On the way back from the meeting, Hoffmann received new radio intercepts. Rennenkampf's marching orders stated the next day's offensive would continue due west, ignoring Samsonov, just as Hoffmann had hoped. No matter the outcome of the impending battle in the south, the Russian First Army would not be a serious concern. A second intercept of Samsonov's own plans made it clear that he would continue his own march northwest, having concluded that the Germans would continue to retreat in front of Tannenberg.
Ludendorff and Hindenburg were skeptical that these intercepts were real, finding it difficult to believe that even one Russian commander would send his messages in the clear, let alone two. Nevertheless they were eventually convinced they were indeed real, and the plans were put into action. I Corps would open its attack on the Russian left flank on 25 August, while orders were sent to XVII Corps to move south and meet the Russian right flank as soon as possible.
Given the need for immediate action was no longer pressing, François once again demanded he be allowed to wait for his artillery supplies. Ludendorff and François began arguing, and eventually François delayed enough to allow the battle to open on 27 August as he had wished.
Due to François' delays, XVII German Corps opened the battle proper. They met the two separated divisions of VI Russian Corps near Seeburg and Bischofstein, turning them both back toward the border in disarray. The right flank of the Second Russian Army was now open. In the meantime, the Russian advance toward Tannenberg continued to be blocked by XX German Corps in front of them. Their only successes were in the center, where XIII Russian Corps advanced towards Allenstein unopposed.
François opened his own attack on the Russian left on the 27th, held by I Russian Corps. His artillery proved to be decisive, and by the night the Russians were falling back. In order to help stabilize the line, Samsonov ordered the seemingly successful XIII Corps to abandon Allenstein and turn southwest to help break through at Tannenberg. By the time this maneuver was complete, the bulk of the Russian Second Army were all in the Tannenberg area, consisting of the newly-arrived XII, XV, and part of XXIII Corps.
By the evening of 28 August the full extent of the danger to the Russians was evident. Their I Corps on the left and VI Corps on the right were both retreating. Meanwhile the center was having serious supply problems and could no longer hope to maintain an offensive. Samsonov had no option but to order a retreat to the southeast and attempt to reorganize near the border. Meanwhile he asked Rennenkampf to ignore Königsberg and turn southwest to help.
It was too late. François by this time had advanced due east to form a line to the south of the Russians between Niedenburg and Willenburg, directly in their line of retreat. At the same time, XVII Corps in the north had moved southwest to meet him. The next day the Russian center met these troops on their way to regroup, and realized they were surrounded. A pocket formed east of Tannenberg, near Frogenau, and was pounded by artillery throughout 29 August.
Attempts by the Russian First Army to come to their aid were also far too late to help. The German cavalry screen proved effective at delaying them, and by the time the battle was already over their closest unit was still to the northwest of the initial contact between XVII German Corps and VI Russian Corps, perhaps as much as 45 miles (70 km) from the trapped Second Army. Other Russian units were scattered back along the line to Königsberg, leaving the First Army itself in a dangerously spread-out position.
By the time the battle ended on 30 August, Samsonov's Second Army was destroyed, with 95,000 Russian troops captured, another 30,000 killed or wounded, and only 10,000 (mostly from the retreating flanks) escaping. The Germans suffered fewer than 20,000 casualties and captured over 500 guns. Sixty trains were required to transport captured Russian equipment to Germany.
The German Eighth Army now faced only the Russian First Army. In a series of follow-up battles, notably the First Battle of the Masurian Lakes, the First Army was severely mauled, and forced back over the pre-war border. Russian forces would not again march on German soil until the end of World War II.
Hindenburg and Ludendorff were both hailed as heroes, although Hoffmann was generally ignored by the press. Apparently not amused by this, Hoffmann later gave tours of the area noting, "This is where the Field Marshal slept before the battle, this is where he slept after the battle, and this is where he slept during the battle." However, Hindenburg is quoted as saying "If the battle had gone badly, the name 'Hindenburg' would have been reviled from one end of Germany to the other."
Ludendorff sent the official dispatch from Tannenberg, and the battle was named Battle of Tannenberg at the direct request of Hindenburg. Hindenburg chose Tannenberg because of its historical significance; it was the location where the Teutonic Knights were defeated by the joint forces of the Kingdom of Poland and the Grand Duchy of Lithuania at the Battle of Grunwald (referred to in German as Schlacht bei Tannenberg - "Battle of Tannenberg"). Interestingly, an ancestor of Hindenburg's had fallen at the battle in 1410.
One interesting side-effect of the battle has since become a point of contention among historians. The three German corps (one complete army) that Moltke had sent to bolster the east never arrived in time to have any effect during the battle. Some scholars have suggested that the removal of an army in the west in the midst of battle was a reason the Schlieffen Plan failed. If true, this would mean that Tannenberg was possibly the successful battle that ultimately lost the war for Germany.
A German monument was completed in 1927. However, it was destroyed by the Soviets and Poles after World War II. Some of its stones were used to build the current Grunwald monument at the site of the 1410 battle.
Ludendorff would later revisit the battle when naming his own political movement, the Tannenbergbund, formed in 1925.