Gorlice – Tarnów Offensive The Gorlice – Tarnów Offensive during World War I started as a minor German offensive to relieve Russian pressure on the Austro - Hungarians to their south on the Eastern Front , but resulted in 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 . Background . In the early stages of the Eastern Front , the German 8th Army had conducted a series of almost miraculous actions against the two Russian armies facing them . After surrounding and then destroying the Russian Second Army at the Battle of Tannenberg in late August , Paul von Hindenburg and Erich Ludendorff wheeled their troops to face the I Army at the First Battle of the Masurian Lakes , almost destroying them before they reached the protection of their own fortresses as they retreated across the border . When the actions petered out in late September , the vast majority of two Russian armies had been destroyed , and all Russian forces had been ejected from the Masurian Lakes area of modern north - east Poland losing almost 200 , 000 soldiers ( killed or taken into captivity ) . Things were not going so well to their south , however . Here the bulk of the Russian army faced an equally large group of Austro - Hungarian units , who started their own offensive in late August , and initially pushed the Russians back well into what is now central Poland . However , a well - executed Russian counterattack in late September pushed them back over their own borders in disarray , allowing the Russians to start the Siege of Przemyśl . The Germans came to their aid by forming up the 9th Army and attacking during the Battle of the Vistula River . Although it was initially successful , the attack eventually petered out and the Germans returned to their starting points . The Russians followed up by redeploying their armies for a further offensive into Silesia , placing both Austria and Germany at risk . When the Central Powers heard of this , the 9th Army was redeployed to the north , allowing them to put serious pressure on the Russian right flank in what developed as the Battle of Łódź in early November . The Germans failed to encircle the Russian units , and the battle ended inconclusively with an orderly Russian withdrawal to the east near Warsaw . Weather prevented further actions over the next months . Battle . General Franz Conrad von Hötzendorf , the Chief of Staff of the Austro - Hungarian Army , originally proposed the idea of breaking up the front line in the area of Gorlice . At first this idea was rejected by German Chief of Staff , Erich von Falkenhayn , who believed that the fate of the war depended on the western front . Later he changed his mind and decided for a major offensive in the Gorlice - Tarnów area , south - east of Krakow , at the far southern end of the Eastern Front . In April 1915 , the recently formed German 11th Army ( 10 infantry divisions under General August von Mackensen ) was transferred from the Western Front . Along with the Austro - Hungarian IV Army ( eight infantry and one cavalry divisions under Archduke Joseph Ferdinand ) , it had to cope with the Russian III Army ( 18½ infantry and five and a half cavalry divisions , under General D . R . Radko - Dmitriev ) , which held that sector . General Mackensen had been given command of both German and Austro - Hungarian forces , and on 2 May , after a heavy artillery bombardment , he launched an attack which caught the Russians by surprise . He concentrated 10 infantry and one cavalry division ( 126 , 000 men , 457 light , 159 heavy pieces of artillery and 96 mortars ) on the of the breakthrough sector of the front line against five Russian divisions ( 60 , 000 men with 141 light and four heavy pieces of artillery ) . The Central Powers shattered the Russian defenses , and the Russian lines collapsed . Radko - Dimitrejew quickly sent two divisions against the German breakthrough , but being ill - prepared they were utterly annihilated without being able to report back to their head quarters . From Russian point of view , both divisions simply disappeared from the map . The Russian III Army left in enemy hands about 140 , 000 prisoners , and almost ceased to exist as a fighting unit . The 3rd Caucasian Corps , for example , brought up to establishment of 40 , 000 men in April , found itself reduced to 8 , 000 . It was thrown into the battle on the San against the Austrian I Army , and succeeded in taking some 6 , 000 prisoners and nine guns . One division was down to 900 men on 19 May . The Russians were forced to withdraw , the Central Powers recaptured most of Galicia , and the Russian threat to Austria - Hungary was averted . Particularly gratifying was the recapture of Przemyśl on 3 June . The same day , fresh offensives were launched : the Austrian IV and VII armies on the flank of the XI Army aiming for the River Dniester . By 17 June , the defenders had pulled back on Lwów ( later Lvov ) , the capital of Galicia , and on the 22nd Austria - Hungary ' s fourth largest city was recaptured . With this loss , which meant that most of Galicia had returned to Austrian hands , the lines stabilized in the south . The penetration progressed about at its deepest , reducing the Polish salient to perhaps ⅓ of its pre - war size . Outcome . Trying to save Russian forces from suffering heavy casualties and gain time needed for the massive buildup of war industries at home , the Russian " Stavka " decided to gradually evacuate Galicia and the Polish salient to straighten out the frontline . A strategic retreat was initiated , which is known as the Great Retreat of 1915 . Warsaw was evacuated and fell on 4 August to the new German 12th Army . At the end of the month Poland was entirely in Austro - German hands , and 750 , 000 Russian prisoners had been taken .