The battle of the Vistula River (28 September-30 October 1914) was a German invasion of Poland launched to relieve the pressure on Austro-Hungary in the aftermath of the Russian victories during the battles of Lemberg.
The German plan involved moving four corps from East Prussia to Silesia, the western frontier of Russian Poland. From there this new Ninth Army would launch an invasion of south west Poland, aimed at Warsaw, which was believed to be lightly defended. The main Russian armies were still deployed along the line of the Carpathians in the south or around East Prussia in the north.
The new German army began to reach Silesia during the third week of September, forming up one a 100 mile front between Posen and Cracow. On 28 September the Ninth Army, 250,000 strong, began to advance north east towards Warsaw and the line of the Vistula.
At this moment there was indeed a gap in the Russian lines, between the Second Army at Warsaw and the Ninth Army on the River San. However, the Russians were also planning to redistribute their armies. They were under pressure from the French to launch an invasion of German Silesia, a heavily industrialised area, and had decided to pull three armies out of the Carpathians to prepare for the move west. The Tenth, First and Second armies were to guard the right flank of the advance, the Third and Eight to remain in the Carpathians and the Fifth, Fourth and Ninth to move west. The decision to form up on the line of the Vistula was made on 22 September.
The Russians soon discovered that there were German troops in Silesia. On 28 September the German advance began, and made rapid progress toward the Vistula. The plan was to capture all of the bridges over the river between Warsaw and the San, to protect the army advancing towards Warsaw.
As the Germans advanced towards the Vistula, the Russian armies began to arrive behind the river. The Fifth Army joined the Second Army at Warsaw, with the Fourth Army to their south. The Ninth Army moved north from the San onto the Vistula.
At the end of the first week of October the Germans were close to the Vistula, but they were unable to take advantage of their slight lead. Instead they found themselves fighting against Russian attempts to take and maintain bridgeheads on the western bank of the river.
The Germans discovered the true situation on 9 October, when they found a set of Russian orders. Eighteen German divisions faced sixty Russian divisions. The Russian plan was for their southern armies to hold the German army on the Vistula while the two armies from Warsaw attacked around the German left flank. If the plan had worked, the Russians might have been able to trap the entire German Ninth against the Vistula.
The German advance continued for several more days. On 12 October General Mackensen’s four divisions were within twelve miles of Warsaw, but the German advance was now mixed with preparations for a retreat.
Those preparations were soon put to the test. When the two Russian armies at Warsaw launched their counterattack, the Russian Second Army easily outflanked the German lines. Further south the Russian Fourth and Ninth Armies launched their own attack against the Austrian First Army along the Vistula. On 17 October Hindenburg and Ludendorff were forced to order a retreat.
The German retreat began in earnest on 18 October, the Russian pursuit on the next day. The Germans conducted a skilful fighting retreat that covered sixty miles in six days. The preparations they had made while moving forward now allowed them to blow bridges and block roads in advance of the Russian troops. By the end of October the Germans were effectively back at their starting line, at the cost of 40,000 men, 16% of the entire force engaged.
The battle of the Vistula is sometimes also known as the first battle of Warsaw. However, this name is often used to describe the second half of the battle, when the Russian armies in Warsaw launched their counterattack and pushed the Germans back towards Silesia.
The battle ended with a major Russian victory. The Germans had escaped with most of their army, but had failed to provide any significant aid to the Austrians, who soon had to abandon any progress they had made further east while the Russians were distracted. At the start of November the Germans were faced with a real danger of invasion by the powerful Russian armies gathering around Warsaw. The only army available to respond to this threat was the Ninth, so over the next ten days that army was rushed by railway from its line south east of Posen to a new line that ran north east from Posen to Thorn. They would then launch a second invasion of Poland (Second battle of Warsaw) that would be rather more effective.