Battle of Tannenberg

The Battle of Tannenberg was the climax to the opening clash between Germany and the Russian Empire following the outbreak of World War I. It was fought between August 26-30, 1914, chiefly around the East Prussian city of Allenstein, and resulted in a crushing victory for the German forces under Field Marshal Paul von Hindenburg and his chief of staff, Erich Ludendorff, with the Russian Second Army almost completely destroyed and its commander, Alexander Samsonov, committing suicide. From a military as well as a political perspective, Tannenberg was among the most important military contests of the war for Germany, as it not only repulsed a Russian invasion of eastern Germany and the threat of a quick defeat, but also elevated Hindenburg and Ludendorff to the status of national heroes. The aura created by their victory would become the basis of their rise to near-dictatorial power in Germany toward the end of the war.

Background

Following the outbreak of war in early August 1914, the German high command, in accordance with the Schlieffen Plan, shifted the vast majority of its troops to the Western Front for a preemptive attack against France. The plan reasoned that Russia, though it had a much larger military, would take considerable time to fully mobilize on account of its great size and primitive infrastructure; therefore the Germans could leave a minimal number of troops on their eastern frontier while achieving a quick victory against the Western Allies, after which the entirety of their forces could be thrown against the Russians. At the outset, then, the border with Russia was defended by a single army stationed in East Prussia, the Eighth, commanded by General Maximilian von Prittwitz und Gaffron. Deployed east of the Vistula River, it had a strength of about 173,000 men.

However, the Russian high command, in order to uphold its alliance with the French, determined to compensate for its weaknesses by mobilizing its available armies at once and sending them forward, while leaving the rest to arm and assemble later. These were the First Army under General Pavel Karlovitch Rennenkampf, stationed in Lithuania and northeastern Poland, and the Second Army under General Alexander Vasilevich Samsonov, massed further south around Warsaw. These two armies, with a combined strength of around 450,000 men, were directed to advance west and north respectively upon East Prussia, converging around the city of Allenstein (modern Olsztyn, Poland). While Rennenkampf marched through the Insterburg Gap between Königsberg and the Masurian Lakes to engage Prittwitz's front, Samsonov would bypass the Lakes from the south to turn the Germans' right flank.

Though the Russians held a significant numerical advantage over the defenders, as well as the strategic value of an unexpectedly early offensive, they were beset by a number of disadvantages: many of the troops were poorly armed and equipped, owing to the incomplete mobilization; their artillery component was notably weak compared to the Germans'; though both Rennenkampf and Samsonov were capable officers, the latter was relatively new to his command, having previously served in the Far East and in Turkestan; and the Russians' supply lines would be inadequate once they advanced into Germany (Russia's use of a different rail gauge meant its cars could not run on German tracks). Another drawback that would prove significant was that the Russian army had neither a proper coding system in use, nor sufficient telephone or telegraph cable to run secure communication lines from front-line units to headquarters. As a result, once on German soil many military communications would be sent as "clear" (that is, uncoded) wireless messages, which the Germans frequently intercepted.

Prelude

Though Russian units had made forays across the frontier as early as August 12, the main offensive opened on the 17th, when Rennenkampf's First Army crossed the border in force, headed for the Insterburg Gap; Samsonov's Second Army invaded from the south two days later. On the first day of his advance, Rennenkampf met resistance at the town of Stallupönen from a portion of the German I Corps under Lieutenant General Hermann von François, which drove the Russian 27th Division back in a chaotic retreat and took some 3,000 prisoners. This attack had been unauthorized by Prittwitz, who ordered François to fall back toward the Eighth Army's main line on the Angerapp River that night; the promising results of Stallupönen, though, and the sluggish pace of the Russian advance, convinced the general to launch a more general counterattack, in hopes of defeating Rennenkampf before Samsonov brought his forces to bear.

Prittwitz attacked near the town of Gumbinnen on the morning of August 20, with generally negative results. The I Corps under François enjoyed some success, assaulting the right flank of the Russian XX Corps and driving it from the field after its artillery ammunition ran out. However, the other units--the XVII Corps under Lieutenant General August von Mackensen and the I Reserve Corps under General Otto von Below--had had to hastily advance from the Angerapp and thus were not in a position to do more than launch frontal attacks, which the Russians easily repulsed. Under heavy bombardment, Mackensen's and Below's troops broke and fled the field, and by nightfall Prittwitz had ordered the whole army to pull back. Though Rennenkampf declined to pursue the retreating troops, due to concern about the state of his supply lines, reports had by now arrived of Samsonov's offensive from the south; in response, Prittwitz gave orders for Eighth Army to retreat all the way to the Vistula, which would mean abandoning most of East Prussia. That same night, he telephoned Field Marshal Helmuth von Moltke, overall commander of the German armies, to explain his intentions.

The planned retreat of the Eighth Army produced consternation at Moltke's headquarters, which had been under the impression that it was holding its own against the invasion. However, Prittwitz's orders were altered again the following day, August 21, when his staff convinced him a southward shift was necessary to block Samsonov's advance before the withdrawal to the Vistula could begin. Most units were accordingly reoriented away from the front of the First Army (which remained quiet), but Prittwitz rejected proposals that he counterattack Samsonov in turn, and in follow-up conversations with headquarters (Oberste Heeresleitung, or OHL), made clear his determination to take up a defensive stance behind the Vistula, and suggested reinforcements from the Western Front would be necessary even to hold that line.

Appointment of Hindenburg

Although the Schlieffen Plan had accepted the likelihood of a brief occupation of Germany's eastern fringe, until all of its military power could be thrown against the Russian foe, the actual prospect of abandoning East Prussia was not acceptable to the political and military leadership, and pressure was rapidly building for a complete change in policy, and if necessary, commanders. Moltke had for some time wanted to replace Prittwitz, whom he considered too old and temperamentally unfit for his job, and the general's vacillating conduct on August 20-21 was not received well at OHL. The conversation of the 21st, in which Prittwitz expressed his decision to give up most of East Prussia and even implied he would retreat from the Vistula without reinforcements, probably sealed his fate. That evening, Moltke decided to relieve both Prittwitz and his chief of staff, Major General Alfred von Waldersee, of their commands.

To lead the Eighth Army, Moltke and OHL selected a retired Prussian general, Paul von Beneckendorff und Hindenburg, who had served on the Army General Staff and later been a corps commander; though 67 years old and not especially brilliant or vigorous, he was regarded as solid and dependable, which was what the Eastern Front needed at the moment. Hindenburg received the request to take command at his home in Hanover the following afternoon and agreed at once.