The third battle of Warsaw of 5 August 1915 saw the Germans occupy Warsaw during the period of success that followed their great breakthrough victory at Gorlice-Tarnow. In the aftermath of the capture of Lemberg (20-22 June) the Germans decided to attempt a double-envelopment of the Russian armies in Poland. A debate between the “easterners” (Hindenburg and Ludendorff) and the “westerners” (Falkenhayn) over the scale of the envelopment to be attempted had resulted in a compromise that saw the northern half of the attack moved too far to the south west to have realistic chance of preventing the Russians from escaping to the east, but it did directly threaten Warsaw.
The German army that had won the victory at Gorlice-Tarnow was now to the south east of Warsaw. It turned north and advanced towards the line Lublin-Kholm from where it threatened to advance east of Warsaw. The northern attack was made by a new Twelfth Army (General von Gallwitz), and was launched towards the Narev River, north of Warsaw.
The attack began on 13 July. By the end of the first week the Germans had reached the Narev. There they were help up for three days, but by the end of July the first German troops had reached the Russian fortress of Novo-Georgievsk, north west of Warsaw. The Russian commander in chief, Grand Duke Nicholas, made the difficult decision to evacuate the city. On 5 August the Russians pulled out of Warsaw, and the Germans were able to capture the city without a fight. Inexplicably the Russians decided to defend the fortress of Novo-Georgievsk, which lost its purpose with the fall of Warsaw, a decision that would cost them 90,000 men.
This was the third of three battles of Warsaw to be fought during the First World War, and numbered as such. Warsaw had been the location of earlier battles, including the battle of Warsaw of 28-30 July 1656, during the First Northern War, and the battle of Warsaw of 6-8 September 1831, during a Polish rebellion against Russian rule.