On August 26, 1914, the Battle of Tannenberg began The 8th German Army defeated the Russian Narev Army. An excerpt from the article:
"How the Battle of Tannenberg Emboldened German Forces at the Start of World War I
The 1914 conflict dealt a defeat so devastating that it drove a Russian general to suicide.
There have been two epic battles at the place known as Tannenberg. The first, in 1410, saw the defeat of a German religious order called the Teutonic Knights at the hands of Slavs and Lithuanians.
Five hundred years later, Germany got its revenge in one of the earliest battles of World War I when a single German army destroyed two much larger Russian invading forces in August of 1914. Even though the German World War I victory took place miles from the 1410 battle, the Kaiser, unable to resist the historical significance, named it Tannenberg.
Russians Invade East Prussia to Divide German Forces
When World War I broke out in 1914, Russia and Great Britain allied with France against the Central Powers of Germany, Austria-Hungary and the Ottoman Empire. Germany’s attack strategy, known as the Schlieffen Plan, was to amass its superior forces in the West and invade France through the neutral state of Belgium. Then the triumphant German armies would ride the rails East to repel the Russians. At least that was the plan.
But the German military machine miscalculated how easy it would be to waltz through Belgium. The neutral nation fought valiantly against an all-out German assault at the 10-day Battle of Liege, the first official battle of World War I, which bought time for British and French troops to shore up their lines of defense.
Meanwhile, Germany had committed seven of its eight armies to the West, believing that it would take at least six weeks for the sluggish Russian army to mobilize its forces and attack in the East. The lone German army dispatched to the Russian border region known as East Prussia was the 8th Army led by General Maximilian von Prittwitz.
“What happened was the Russians mobilized a lot quicker than the Germans expected,” says Jay Lockenour, a military historian at Temple University. “Also, the 8th Army was the weakest of the German armies. It was a lot of reservists and garrison troops, people normally assigned to defend fixed positions.”
When the Germans learned that the Russians were invading East Prussia with two armies, one in the North and another in the South, they ordered Prittwitz to attack the northern Russian 1st Army at what became known as the Battle of Gumbinnen on August 20, 1914. Both sides suffered heavy losses and Prittwitz, envisioning a second Russian army on its way, lost his nerve.
“Prittwitz was no slouch,” says Lockenour, “but he had suffered defeat at the Battle of Gumbinnen and decided that retreat was the only option in the face of these two armies coming at him out of Russia.”
The German brass pulled Prittwitz from command and replaced him with the legendary Paul von Hindenberg (brought out of retirement) and a military mastermind named Erich Ludendorff, fresh from a German victory at the Battle of Liege. Retreat was not an option."