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.

[7] At the same time, the Austro-Hungarian Army launched a series of attacks collectively known as the Battle of Galicia that were initially successful but soon turned into a retreat that did not stop until reaching the Carpathian Mountains in late September.

In fierce winter fighting General Franz Conrad von Hötzendorf, the chief of staff of the Austro-Hungarian Army, attacked the Russians in an attempt to push them back.

On the other hand, I should like to submit the following plan of operations for your consideration...An army of at least eight German divisions will be got ready with strong artillery here in the west, and entrained for Muczyn-Grybów-Bochnia, to advance from about the line Gorlice-Gromnik in the general direction of Sanok."

Buttar goes on to state, "Impressed by the resilience of German troops on the Western Front when the French attacked in late 1914 and again in early 1915, Falkenhayn had adopted the proposal of Oberst Ernst von Wrisberg...and ordered some divisions to give up one of their four regiments and to reduce their artillery batteries from six guns to four."

Mackensen was provided with a strong train of heavy artillery commanded by Generalmajor Alfred Ziethen, which included the huge German and Austro-Hungarian mortars that had crushed French and Belgian fortresses.

[14] On 22 April, the Germans launched the first poison gas attack near Ypres, divulging what might have been a decisive weapon merely to distract the Allies in the west.

Mackensen had ten infantry and one cavalry divisions (126,000 men, 457 light guns, 159 heavy pieces, and 96 mortars) along the 42 km (26 mi) length of the breakthrough sector.

[15] The Russian supreme commander, the Grand Duke Nicholas Nicholaevitch, learned that Germans had arrived on their flank but did not make a counter-move.

Mackensen had already defined "lines that should be reached in a uniform and if possible simultaneous manner, without preventing the troops from collectively moving on to secure the next sector where possible."

Mackensen then issued orders for the advance upon the River Wisłoka as the next objective, which constituted the Russian third and final line of defense.

Grand Duke Nicholas permitted a limited withdrawal, but rejected advice to construct a well fortified position far behind the frontline and then to pull back to it.

At this point the Russian counterattacks grew ever more desperate, often throwing brand new recruits into battle, some armed only with grenades or wooden clubs.

This Third Army southern flank, led by Vladimir Olukhov, was supposed to prevent the 'Mackensen phalanx' from gaining any additional territory.

[6]: 227–229, 236–237 The Central Powers' next objective was a continued advance towards the east from a bridgehead at Magierów, and the ultimate recapture of Lemberg, which would sever lines of communication between the Russian Northwest and Southwest Fronts.

The German attack commenced again on 19 June, after the previous day was spent bringing forward their heavy artillery with matching aerial reconnaissance.

[20] The battles on the Bug and Zlota Lipa Rivers ended the Gorlice–Tarnów offensive, during which the armies of the Central Powers managed to inflict the largest defeat on the troops of the Russian Empire.

[21] Heavy сasualties in the May battles forced the Russian armies to retreat from Galicia in early June 1915, and so hastily that the fortified positions prepared in the rear remained abandoned.

The low stability of the troops of the Russian 8th Army, which left Lvov on June 22, became the reason for sharp reprimands from the front headquarters.

Skillfully directed fire from hand weapons was very effective, and massive frontal assaults cost the victorious troops dearly, which was reflected in the gradual narrowing of the breakthrough front.

For 10 weeks, the Russian armies of the Southwestern Front and the left flank of the armies of the Northwestern Front were thrown back in Galicia – across the Bug, Zlota Lipa and Dniester rivers, retaining only a small part of the Austria-Hungary’s territory, and in the Kingdom of Poland they retreated beyond the Vistula to Józefów, across the Tanew River, to Krasnystaw and Hrubieszów – approximately to the lines from which the Russian invasion of Galicia began in August 1914.

The reasons for the defeat of the Russian armies in the 1915 campaign, which became the most important operation, were usually called the overwhelming numerical superiority of the Central Powers, insufficient technical equipment and lack of artillery ammunition, and the excessive persistence of the Russia Headquarters in defending the conquered Galicia.

One of the first researchers of the First World War in Russia, Andrei Zayonchkovski, saw the causes of defeats primarily in the shortcomings of the Russian troops command and control system: the lack of a single plan of action (and as a result, the initiative was ceded to the enemy), neglect of assessing the capabilities of the terrain and the position of the troops (as a result – "throwing suitable reserves from side to side"), weakness of technical training (creation of reserves, organization of supplies), biased attitude towards the enemy and his underestimation, distrust of the troops and individual commanders.

… and the troops with their commanders", and "the doctrine of a concentrated strike, preached in the Russian army throughout the nineteenth century, in practice resulted in separately operating tentacles.

Warsaw was evacuated and fell to the new Twelfth German Army on 5 August, and by the end of the month Poland was entirely in Austro-German hands (see Bug-Narew Offensive).