The Battle of Stalluponen was the first battle on the Eastern Front of World War 1. It was fought on August 17, 1914, between a corps of the German Eighth Army and Russian General Rennenkampf's First Army.
The Battle
Russia had planned to invade East Prussia with two armies: Rennenkampf's First Army from the north and General Samsonov's Second Army from the south. Rennenkampf's army entered East Prussia on August 17, 1914, and General Hermann von Francois, commander of the I Corps of the German Eighth Army, attacked them.
Francois's attack was successful, and he drove the Russians back to the frontier, capturing 3,000 prisoners. However, General von Prittwitz, commander of the German Eighth Army, was concerned that Francois's forces were in danger of being encircled by Rennenkampf's larger army. He ordered Francois to call off his attack, and Francois's corps withdrew to Gumbinnen.
Rennenkampf's army resumed its march westward into East Prussia, and Francois urged Prittwitz to launch a new offensive against Rennenkampf.
Prittwitz, encouraged by Francois's initial success, agreed and authorized a much larger attack on the Russian First Army three days later, on August 20, at the Battle of Gumbinnen.
The Battle of Gumbinnen was a German victory, and it forced Rennenkampf to withdraw from East Prussia. However, the battle was costly for both sides, and it did not end the threat of a Russian invasion.