First Battle of Warsaw 19–30 October 1914

In September 1914 the Russians gained an intelligence advantage over the enemy, when papers recovered from a dead German officer revealed the massing of Central Powers forces in Silesia. Forewarned of impending attack, the Russians began to fall back towards the River Vistula. The German mastery of their enemies’ military secrets now reasserted itself; having quickly cracked newly introduced Russian ciphers, the Germans learned of their plans to encircle the advancing Central Powers forces in emulation of Tannenberg. Hindenburg reorganized his forces to avert this risk but then, on 19 October 1914, the Russians launched a frontal assault across the Vistula against opposing Austro-Hungarian forces. Under intense pressure the whole frontline was forced back some 37 miles (60 km). The victory, although hardly emphatic, gave a boost to Russian morale, but the Central Powers retreated in good order, laying waste the ground behind and thwarting any decisive Russian follow-up.