Gorlice–Tarnów offensive

Gorlice–Tarnów offensive
	Part of the Eastern Front of World War I
	; Gorlice–Tarnów breakthrough; and Russian withdrawal
Date	2 May – 13 July 1915
Location	Gorlice and Tarnów area, south-east of Kraków, Galicia, Austria-Hungary (present-day Poland and Ukraine)
Result	Central Powers victory Great Retreat; Liberation of Galicia
Belligerents
German Empire; Austria-Hungary	Russian Empire
Commanders and leaders
Erich von Falkenhayn; August von Mackensen; Hans von Seeckt; E. von Böhm-Ermolli; Svetozar Boroević; Paul von Brlog; Archduke Joseph Ferdinand	Grand Duke Nicholas; Nikolay Ivanov; Radko Dimitriev
Units involved
XI Army; South Army; II Army; III Army; IV Army; VII Army	III Army; IV Army; VIII Army; XI Army; IX Army
Strength
1,613,360 men; 1,884 machine guns ; 3,259 guns; 10 infantry divisions; 8 infantry divisions, 1 cavalry division;	1,424,158 men; 1,768 machine guns; 2,383 guns
Casualties and losses
520,000	410,000–1,019,953 killed and wounded; 250,000 captured; 224 guns, 600 machine guns

The Gorlice–Tarnów offensive during World War I was initially conceived as a minor German offensive to relieve Russian pressure on the Austro-Hungarians to their south on the Eastern Front, but resulted in the Central Powers' chief offensive effort of 1915, causing the total collapse of the Russian lines and their retreat far into Russia. The continued series of actions lasted the majority of the campaigning season for 1915, starting in early May and only ending due to bad weather in October.

Mackensen viewed securing a breakthrough as the first phase of an operation, which would then lead to a Russian retreat from the Dukla Pass, and their positions north of the Vistula.^: 201