The Russian “Plan A” involved an attack on the Austrian Empire as soon as enough troops had been mobilised to mount the offensive. The attack began on 17 August 1914.
The Russian 4th Army under General Ivanov attacked near Lublin, supported by the 3rd Army and the 8th Army under General Brusilov. The Austrian 2nd and 3rd Armies fell back slowly. On 30 August the Russians captured Lemberg (now Lvov).
On 4 September the Austrians launched a large scale attack on the Russian centre designed to halt the Russian advance. The attack failed and the Austrians began a retreat that soon became a rout as the supply system collapsed and soldiers fled.
By 20 September the Austrians had lost 110,000 men killed or wounded and 220,000 men taken prisoner. Another 100,000 men were cut off at Przemysl. The Russians were advancing quickly through Galicia towards the vital German industrial area of Silesia.
German commander in the east, von Hindenburg, took two thirds of his men from East Prussia and formed them into a new force, the 9th Army, to protect Silesia. Again, swift transport by rail allowed the Germans to get in position in time.
from "100 Facts on World War I" by Rupert Matthews
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