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.

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.

The Russian army wasn’t nearly as experienced and well-trained as its German foe, and that led to some critical mistakes. The biggest Russian error was to broadcast their orders over open radio frequencies, the result of confusion over encoded messages. By intercepting these messages, the Germans learned that the Russian 1st Army wasn’t chasing down the German 8th Army as expected, but rather turning North toward the Prussian city of Königsberg.

Ludendorff, the brilliant German strategist, saw an opportunity. The two Russian armies were separated by challenging terrain known as the Masurian Lakes which slowed their progress. Knowing that the Russian 1st Army was on its way North to Königsberg, Ludendorff and Hindenberg decided to commit most of the German 8th Army to strike the Russian 2nd Army south of the lakes.

“I argue that Ludendorff is the brains of the operation,” says Lockenour, who wrote a book called Dragonslayer: The Legend of Erich Ludendorff in the Weimar Republic and Third Reich. “He was an incredibly experienced staff officer and had already won the Pour le Mérite cross, similar to the Congressional Medal of Honor, for his leadership at Liege.”

The Russian commanders weren’t amateurs, but they were hampered by poor communications, slow supply routes and the frustrations of moving a large army (plus heavy artillery) on foot and horseback through difficult terrain. General Alexander Samsonov, in charge of the Russian 2nd Army in the South, walked right into Ludendorff’s trap and allowed his men to be completely encircled.

“Then the Germans launched two flank attacks,” says Lockenour. “Imagine this Russian army as a bulge pressing into Germany and the Germans strike at a point where the bulge begins and cut off the vast majority of the Russian forces in the middle. Because of communication problems, the Russian commanders didn’t know that a major attack on their flank was underway until half a day too late.”

Samsonov was in command of 150,000 men in the Russian 2nd Army and less than 10,000 made it back to Russia, says Lockenour. An estimated 50,000 Russian troops were killed in panicked fighting and 92,000 more were taken by Germany as prisoners of war.

Unable to face the czar and explain the horribly lopsided defeat at Tannenberg, Samsonov walked alone into the woods and killed himself with his officer’s pistol.

“That was not uncommon, even into the Second World War, for commanders to take personal responsibility for major defeats,” says Lockenour.

But the troubles for Russia weren’t over yet. Fresh from the victory at Tannenberg, the German 8th Army marched north and routed the Russian 1st Army at the Battle of Masurian Lakes. The Russian army retreated in disarray, losing tens of thousands as prisoners of war.

“The Russian 1st and 2nd Armies effectively ceased to exist after these two battles,” says Lockenour. “It was a devastating defeat. The Russians faced off against the Germans with superior numbers and got nothing—worse than nothing.”

Hindenburg and Ludendorff, now national heroes in Germany, petitioned the Kaiser to name the initial victory the Battle of Tannenberg simply for the “mythical benefit” of German retribution for the 1410 defeat, says Lockenour. After Germany ultimately lost World War I, Tannenberg took on even greater symbolic significance.

“Because the battle took place on German soil, it provided fuel for Germany’s completely disingenuous argument that the war was forced upon them,” says Lockenour, “that the Russian colossus invaded and it was a defensive war.”

In the 1920s, an increasingly bitter Germany built a massive memorial structure at Tannenberg and Hindenberg’s body was eventually interred there (against his family’s wishes, says Lockenour). Adolf Hitler renamed it the Reichsehrenmal “Reich Memorial” but had it destroyed in 1945 before the invading Russian army could burn it themselves.